277 Silicone O-Ring 70A Durometer 11-1/2 in ID Pack of 10 - Durable

In this review the Mr O-Ring 277 Silicone O-Ring is assessed for workshop and maintenance use where heat tolerance and ozone resistance matter most. The bottom line: this pack of ten red, 70A durometer silicone o-rings is aimed at technicians, hobbyists and facilities managers who need reliable sealing across a wide temperature range; the single biggest reason to buy is its combination of AS568 sizing accuracy and silicone's exceptional performance from -60C to 225C, which makes it a safe, versatile choice for many static and low-movement seals.

Key Features

• 277 Silicone material: provides excellent heat, ozone and corona resistance so seals last in hot or outdoor environments.
• 70A durometer: balances flexibility and firmness for dependable compression in static and mild-dynamic sealing applications.
• Pack of 10: gives spare parts on hand for routine maintenance or small production runs without frequent reordering.
• AS568 compliant sizing: nominal and actual dimensions match standard sizes so replacements fit predictable housings and grooves.
• Wide temperature range: rated from -60C (-76F) to 225C (437F), suitable for engine bay, oven or exterior uses where temperatures vary widely.
• FDA-compliant: safe for incidental contact applications where regulatory compliance matters.

Who It's For

This product is best for maintenance technicians, HVAC and plumbing professionals, small engine repairers and hobbyists who need a reliable silicone seal rated for broad temperatures and exposure to ozone, mild water and common mineral oils. The pack size and standard AS568 dimensions make it convenient for shops that perform routine replacements.

Those seeking high-wear, dynamic sealing under heavy friction or high-pressure hydraulic seals should look at other elastomers with higher tensile strength and wear resistance, since silicone has lower wear resistance compared with some fluorocarbon or nitrile compounds.

Pros & Cons

Pros

• Excellent thermal and ozone resistance suitable for hot or outdoor installations.
• Standard AS568 sizing and measured actual dimensions make it easy to swap into existing grooves.
• Pack of ten offers value and convenience for maintenance and spare-part inventories.
• FDA-compliant and compatible with many mineral oils and diluted salt solutions.

Cons

• Lower tensile strength and wear resistance than some alternative elastomers, so not ideal for heavy abrasion or high-friction dynamic seals.

Specifications

Material	277 Silicone
Durometer	70A
Nominal dimensions	11-1/2 in ID, 11-3/4 in OD, 1/8 in CS
Actual dimensions	11.484 in ID, 11.762 in OD, 0.139 in CS
Metric dimensions	291.69 mm ID, 298.75 mm OD, 3.53 mm CS
Temperature range	-60C (-76F) to 225C (437F)
Pack size	10 o-rings

Our Verdict

The Mr O-Ring 277 Silicone 70A pack is a sensible purchase for anyone needing accurate, heat-resistant replacement o-rings in a commonly used AS568 size. It represents good value for maintenance shops and hobbyists who prioritize temperature range and ozone resistance, though users with heavy-duty dynamic wear needs should select a harder-wearing compound.

Frequently Asked Questions

Are these o-rings the stated dimensions?
Yes, the listing provides both nominal and measured actual dimensions so you can confirm fit for standard AS568 grooves.

Can they be used with engine oil?
They perform well with engine and transmission mineral oils, but check compatibility for specific synthetic fluids or aggressive chemicals.

Do they tolerate outdoor exposure?
Yes, silicone offers good ozone and weather resistance suitable for many exterior sealing applications.