{"product_id":"339-viton-o-ring-75a-durometer-3-1-4-in-id-x-3-5-8-in-od-durable","title":"339 Viton O-Ring 75A Durometer, 3-1\/4 in ID x 3-5\/8 in OD - Durable","description":"\u003cp\u003eIn this review the 339 Viton O-ring is recommended for technicians, hobbyists, and maintenance teams who need a durable seal that resists heat, fuels, and many chemicals. The single biggest reason to buy is material performance: made of Viton fluorocarbon elastomer with a 75A shore durometer, it maintains seal integrity across a wide temperature range and in contact with common fuels and aromatic hydrocarbons. Reviewers who replaced worn fuel bottle seals or barrel seals found the fit and leak resistance particularly reliable.\u003c\/p\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Viton fluorocarbon elastomer provides superior resistance to heat, fuels, and many aggressive chemicals compared with general-purpose elastomers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTemperature Range:\u003c\/strong\u003e Usable from -15 degrees F to 400 degrees F so it withstands demanding thermal cycles in engines and industrial systems.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDurometer:\u003c\/strong\u003e 75A hardness balances flexibility and penetration resistance so the ring keeps shape while maintaining a tight seal under pressure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCross-Section:\u003c\/strong\u003e Round profile creates a reliable seal between overlapping cylindrical surfaces, ideal for bottle necks, barrels, and fittings.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eChemical Compatibility:\u003c\/strong\u003e Compatible with fuels, aromatic and aliphatic hydrocarbons, silicone oil, and chlorinated hydrocarbons for broad application use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandards:\u003c\/strong\u003e Meets Aerospace Standard AS568A sizing conventions, which helps when replacing common specified O-rings.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWho It's For\u003c\/h2\u003e\n\u003cp\u003eThis O-ring is best for mechanics, field technicians, and DIYers who need a dependable replacement for fuel system seals, hydraulic fittings, or vacuum and ozone-exposed components. It suits applications where heat and hydrocarbon exposure are expected, such as fuel bottles, small engines, and some firearm component seals.\u003c\/p\u003e\n\u003cp\u003eUsers who require compatibility with low molecular weight organic acids, strong alkalis, ammonia gas, or glycol-based brake fluids should look elsewhere, since Viton is vulnerable to those chemistries. Also avoid using it where continuous exposure to super-heated steam is anticipated.\u003c\/p\u003e\n\u003ch2\u003ePros \u0026amp; Cons\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePros\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eExcellent heat and fuel resistance keeps seals intact under high temperature and gasoline exposure.\u003c\/li\u003e\n\u003cli\u003eCustomers report accurate fit and reliable leak resistance for common replacements like fuel bottle and barrel seals.\u003c\/li\u003e\n\u003cli\u003e75A durometer offers a good balance of durability and sealing performance for pressurized joints.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCons\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eNot chemically compatible with some acids, amines, and glycol-based fluids, limiting use in certain brake or chemical systems.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003eViton (fluorocarbon elastomer)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eColor\u003c\/td\u003e\n\u003ctd\u003eBlack\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCross-Section\u003c\/td\u003e\n\u003ctd\u003eRound\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInner Diameter (ID)\u003c\/td\u003e\n\u003ctd\u003e3-1\/4 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOuter Diameter (OD)\u003c\/td\u003e\n\u003ctd\u003e3-5\/8 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWidth (cross-section)\u003c\/td\u003e\n\u003ctd\u003e3\/16 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDurometer\u003c\/td\u003e\n\u003ctd\u003e75A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTemperature Range\u003c\/td\u003e\n\u003ctd\u003e-15 F (-26 C) to 400 F (205 C)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch2\u003eOur Verdict\u003c\/h2\u003e\n\u003cp\u003eThe 339 Viton O-ring is a practical, cost-effective choice for anyone needing a heat- and fuel-resistant seal that holds up in demanding conditions. Its 75A hardness and Viton compound make it especially suitable for fuel system replacements and high-temperature applications, delivering reliable leak resistance and long service life when used within its compatibility limits.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eCan this O-ring be used with gasoline and diesel?\u003c\/strong\u003e\u003cbr\u003eYes. Viton is compatible with many fuels and aromatic hydrocarbons, making this O-ring suitable for gasoline and similar fuels.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill it work at high temperatures around 400 F?\u003c\/strong\u003e\u003cbr\u003eYes. The ring is rated up to 400 F (205 C), which covers many engine and industrial thermal conditions.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs it suitable for brake fluid systems?\u003c\/strong\u003e\u003cbr\u003eNo. Viton is vulnerable to glycol-based brake fluids and should not be used where those fluids are present.\u003c\/p\u003e","brand":"Mr O-Ring","offers":[{"title":"Default Title","offer_id":48608372359387,"sku":"B000FN102O","price":36.29,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0724\/1043\/1707\/files\/81iyYJCP7YL._SL1500_8a716575-7b65-4aab-8174-4f8e9c85a89f.jpg?v=1778377536","url":"https:\/\/gearmusthave.com\/products\/339-viton-o-ring-75a-durometer-3-1-4-in-id-x-3-5-8-in-od-durable","provider":"GearMustHave","version":"1.0","type":"link"}