Specification guide
USP Class VI Silicone and O-Rings: What It Means
USP Class VI is the most demanding of the six plastic classes in United States Pharmacopeia chapter 88, which sorts materials by how living tissue reacts to them; a silicone or other elastomer compound meets it when its maker has that exact compound tested and it passes. It is required when the drawing, the purchase order or the device maker's biocompatibility plan names it, most often for medical devices and pharmaceutical processing equipment. The listing belongs to the compound and its maker, so an O-ring meets it only when it is molded from the tested compound and the paperwork names that compound.
What USP Class VI tests
USP chapter 88 covers in vivo tests, run in living animals, and sorts plastics into Classes I to VI by how tissue responds; Class VI asks for the most. Rogers Corporation's technical bulletin on the subject names the three tests behind it: a systemic injection test and an intracutaneous test, both run on extracts of the material, and an implantation test in which strips of the material are placed in tissue. The chapter is written around plastics, and elastomer makers test their compounds to it as well, as the maker sheets further down show. USP chapter 87 is the separate in vitro chapter, a cytotoxicity test, and several of those sheets list the two side by side.
Two things follow from how the tests work. The result describes one compound as it was made and tested, so a different compound is not covered, even one from the same family in the same color. And the tests say nothing about sealing performance: the temperature range, the media and the sterilization methods still come from the compound's datasheet.
USP Class VI, FDA, ISO 10993 and NSF compared
| Requirement | Issued by | What it covers | Evidence a buyer receives | Typical use | Source |
|---|---|---|---|---|---|
| USP Class VI | United States Pharmacopeia, chapter 88 | Biological reactivity of the material in living tissue, by systemic injection, intracutaneous and implantation tests | The compound maker's statement, or the laboratory report behind it, naming the compound | Medical devices and pharmaceutical processing | USP chapter 88 (title); Rogers bulletin 180-432 |
| FDA 21 CFR 177.2600 | US Food and Drug Administration (a regulation, not a certificate) | Permitted ingredients and extraction limits for rubber articles in repeated food contact | The compound maker's statement of compliance naming the compound; the FDA approves neither compounds nor parts | Food processing and packaging equipment | 21 CFR 177.2600 (title) |
| ISO 10993 | ISO | A series on the biological evaluation of a medical device; Part 1 sets how that evaluation runs within a risk management process | Test reports for the parts of the series the program names, such as parts 5 and 10 | Medical devices; Rogers rates it more demanding than USP Class VI | ISO catalog page for ISO 10993-1; Rogers bulletin 180-432 |
| NSF/ANSI 51 | NSF, a third-party listing body | Materials used in food equipment | An NSF listing of the compound or product | Commercial food equipment | NSF/ANSI 51 (title) |
| NSF/ANSI 61 | NSF | Drinking water system components | An NSF listing | Potable water service | NSF/ANSI 61 (title) |
One compound can carry several of these at once. Parker®'s E3609-70 EPDM, per its datasheets, lists FDA compliance, NSF 51 and 61, USP Class VI and USP chapter 87, and a separate Parker sheet reports ISO 10993-5 and -10 results for it. Each listing still has to be named on the paperwork, because evidence for one is not evidence for another. The FDA and food-grade O-ring guide covers the food-contact documents in more depth.
Which compounds are offered with USP Class VI
USP Class VI grades exist in several families, but only as named compounds, so the family narrows the search and the compound number settles it. Each row names a maker's own document; the maker's current sheet for the grade you order governs.
| Family | Maker's compound or grade | Listings the maker names for it | Source |
|---|---|---|---|
| Silicone (sheet and foam) | BISCO® MS silicones, Rogers; platinum-cured, per the maker | USP Class VI, ISO 10993 and 21 CFR 177.2600 for select grades, each marked as testing in process on the 2023 sell sheet | Rogers sell sheet 180-402 (2023) and bulletin 180-432 (2024) |
| EPDM | Parker E3609-70 | USP Class VI and USP chapter 87, with FDA, NSF 51 and NSF 61; ISO 10993-5 and -10 results on a separate sheet | Parker E3609-70 datasheets |
| FFKM | Simriz® 484, Freudenberg | 3-A, FDA and USP Class VI | Freudenberg Simriz FFKM brochure |
| FFKM | Isolast® J9515, and J9516 in white, Trelleborg | FDA, USP Class VI and 3-A | Trelleborg Isolast capabilities brochure |
| FFKM | Chemraz® SD517, Greene Tweed | USP chapters 87 and 88 (Class VI), FDA under 21 CFR 177.2400, the regulation for perfluorocarbon-cured elastomers, and 3-A | Greene Tweed Chemraz SD517 data sheet |
For a silicone O-ring, ask for the statement from the maker of the O-ring compound: the sheet and foam grades in the first row do not cover a molded ring. The silicone O-ring page, the EPDM O-ring page and the FFKM O-ring page carry each family's range and callouts, and the Simriz page carries the grade figures for that line. Foam and sheet gaskets for devices are on the medical foam gasket page.
When USP Class VI is required
It is required when a document you work to names it: the drawing, the purchase order, or the device maker's biocompatibility plan. That is most common for seals in medical devices and in pharmaceutical and biotech process equipment. Food equipment normally names 21 CFR 177.2600, NSF/ANSI 51 or a 3-A standard instead, so USP Class VI is not a food-contact requirement on its own. Rogers draws the line by device: its bulletin puts the lower-risk Class I devices within reach of a USP Class VI result and sends devices that stay implanted to ISO 10993. The device maker evaluates the finished device, and a compound's Class VI result is one input to that evaluation, not the evaluation itself.
The medical and pharmaceutical industry page covers the other seals and gaskets those programs buy.
What to ask for, and what ships with the order
- The compound maker's USP Class VI statement, a letter or certificate naming the compound number, or a summary of the laboratory report behind it. A statement for the family, or for another compound, does not cover your part.
- The compound datasheet, for the temperature range, the media and the sterilization methods the compound is rated for; its compliance line should name USP Class VI and the compound number.
- A certificate of conformance. Conquest's certificate of conformance ships with every order and names the part number, the specification, the manufacturer, the lot, the quantity and the manufacturer's cure date.
- The manufacturer's certification, on the raw material or from the maker of the finished part, when your program asks for it; put it on the purchase order.
- Any other listing by name, such as USP chapter 87, a part of ISO 10993, FDA or NSF, because each one is a separate document.
Conquest does not test or certify biocompatibility; the maker's statement ships as the maker issued it. The certificate of conformance guide shows how the documents fit together, and the compliance documents page lists the supplier statements available on request.
How to put USP Class VI on an RFQ
| Item | Why it matters | Example |
|---|---|---|
| Size | The dash number or the drawing fixes the part; the compound does not change the size | AS568-214, or the drawing number and revision (AS568 chart) |
| Family and compound | The Class VI result belongs to one compound | Silicone, with the maker's compound number as the print gives it |
| The requirement | USP Class VI is one test program; name any other the program needs | USP Class VI and USP chapter 87 |
| Documents | Each document is issued separately | The maker's USP Class VI statement naming the compound, and a certificate of conformance |
| Service | The datasheet's range, media and sterilization methods govern | Steam sterilization; saline and alkaline cleaners |
| Static or dynamic | Silicone is a static-seal material | Static face seal on a pump housing |
| Quantity | Sets the order and any repeat supply | The order quantity, and the annual use if it repeats |
If the print names only a family, say so, and the quote names the documented compounds available. The quote form takes the drawing and these details together, and a person replies within one business day.
BISCO is a trademark of Rogers Corporation; Parker is a trademark of Parker Hannifin Corporation; Simriz is a trademark of Carl Freudenberg KG (Freudenberg Sealing Technologies); Isolast is a trademark of Trelleborg Sealing Solutions; Chemraz is a trademark of Greene Tweed. No affiliation or endorsement is implied.
Sources
- United States Pharmacopeia, general chapters 87 (Biological Reactivity Tests, In Vitro) and 88 (Biological Reactivity Tests, In Vivo) (titles only)
- Rogers Corporation, USP Class VI and BISCO MS Silicone Compliance, technical bulletin 180-432 (2024), read 2026-09-25
- Rogers Corporation, BISCO MS Silicones sell sheet 180-402 (2023), read 2026-09-25
- Parker E3609-70 compound datasheets: the ethylene propylene O-ring sheet for drinking water and medical service, and the ISO 10993-5 and -10 compliant EPDM sheet ORD 5772, read 2026-08-13
- Freudenberg-NOK, Simriz FFKM brochure 71 US 011 (grade table), read 2026-09-14
- Trelleborg Sealing Solutions, Advanced Isolast capabilities brochure (2021), read 2026-09-14
- Greene Tweed, Chemraz SD517 data sheet (02/20), read 2026-09-25
- ISO 10993-1, Biological evaluation of medical devices, Part 1 (ISO catalog page), read 2026-09-25
- Parker O-Ring Handbook ORD 5700 (2021 printing), sections 2.2.13 and 3.10.2 (silicone as a static seal), read 2026-09-27
- 21 CFR 177.2600; NSF/ANSI 51; NSF/ANSI 61; 3-A Sanitary Standards (titles only)
Reviewed by Grant Midstokke, Conquest Seal Corporation. Last updated . Spec values in this guide are drawn from the sources listed above; the compound datasheet and your application conditions govern the final choice.
Frequently asked questions
Is a white silicone O-ring USP Class VI?
No. Color is a pigment choice. Only the compound maker's USP Class VI statement for the compound number on your order shows it.
Do I need USP Class VI for food equipment?
Usually not. Food equipment normally names 21 CFR 177.2600, NSF/ANSI 51 or a 3-A standard; USP Class VI is used for medical and pharmaceutical service.
What is the difference between USP chapter 87 and chapter 88?
Chapter 87 is the in vitro cytotoxicity chapter. Chapter 88 holds the in vivo tests that define Classes I to VI, Class VI among them, and a compound sheet that lists both is naming two separate test programs.
Is USP Class VI the same as ISO 10993?
No. They are separate test programs; Rogers' bulletin ranks ISO 10993 as the more demanding of the two and names it for implanted devices. The device program names the one it needs, or both.
Does Conquest certify O-rings to USP Class VI?
No. The listing belongs to the compound and its maker, who has the tests run. Conquest supplies parts in documented compounds with the maker's statement and a certificate of conformance.
Can one compound be FDA compliant and USP Class VI?
Yes. Parker's E3609-70 EPDM datasheets list FDA compliance, NSF 51 and 61 and USP Class VI together. Each listing still has to be named on the paperwork.
Which families come in USP Class VI grades?
Among the maker documents cited here: silicone sheet and foam (BISCO MS), EPDM (E3609-70) and FFKM (Simriz 484, Isolast J9515 and J9516, Chemraz SD517). Every family is offered compound by compound, so ask for the compound number.
Related guides
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