Mr O-Ring 157 Viton O-Ring 4-1/2 in ID - Pack of 25

In this review the reviewer focuses on the Mr O-Ring 157 Viton O-Ring pack of 25 and who will get the most value from it. The bottom line: this set is for technicians, hobbyists and maintenance teams who need reliable, high-temperature sealing in petroleum and chemical environments; the single biggest reason to buy is the material performance - a 90A durometer Viton (FKM) compound that resists fuels, oils, ozone and high heat. The reviewer found the nominal and actual sizes close enough for AS568 applications and appreciated the metric equivalents provided for planning and inventory.

Key Features

• Material: Viton (FKM) delivers strong resistance to fuels, mineral oils and many organic solvents for longer service life in harsh fluids.
• Hardness: The 90A durometer balances elasticity and compression set resistance so seals maintain contact under pressure and temperature changes.
• Temperature range: Rated from -26C to 232C (-15F to 450F), useful for hot engine bays, ovens and high temperature process lines.
• Size accuracy: Actual dimensions (4.487 in ID, 4.693 in OD, 0.103 in CS) closely match nominal sizes for easy replacement of AS568-standard parts.
• Pack quantity: Comes as a pack of 25, which is convenient for preventive maintenance kits or repeated repairs without frequent reordering.
• Chemical compatibility: Performs well in petroleum, diesel, biodiesel blends, methanol/ethanol blends, silicone oils and high vacuum applications.

Who It's For

This product suits industrial mechanics, automotive technicians and OEM maintenance staff who work with fuel systems, hydraulic lines or equipment exposed to high temperature or aggressive fluids. The combination of Viton chemistry and 90A hardness makes it a practical choice where resistance to oils, fuels and heat is required.

It is less suitable for applications needing very soft seals, food-grade certification, or specialized low-temperature elastomers below the stated range. Buyers requiring a different durometer or non-fluorocarbon compound should look elsewhere.

Pros & Cons

Pros

• Excellent chemical and high-temperature resistance from Viton FKM for durable sealing in aggressive environments.
• 90A durometer offers a good balance of firmness and flexibility for many industrial sealing tasks.
• Pack of 25 provides value for maintenance programs and reduces downtime due to reordering.
• Actual and metric measurements are provided, simplifying parts matching and inventory tracking.

Cons

• Viton is not ideal for applications that require FDA food-grade elastomers or very soft seals below 90A.

Specifications

Material	Viton (FKM)
Durometer	90A
Nominal dimensions	4-1/2 in ID, 4-11/16 in OD, 3/32 in CS
Actual dimensions	4.487 in ID, 4.693 in OD, 0.103 in CS
Metric dimensions	113.97 mm ID, 119.21 mm OD, 2.62 mm CS
Temperature range	-26C (-15F) to 232C (450F)
Pack quantity	25 pieces

Our Verdict

The Mr O-Ring 157 Viton O-Ring pack is a practical, cost-effective choice for professionals who need durable seals resistant to fuels, oils and high temperatures; the 90A durometer and accurate dimensions make it a reliable replacement for AS568 applications and a good value when bought in a pack of 25.

Frequently Asked Questions

Are these O-rings compatible with diesel and biodiesel blends?
Yes, Viton FKM is listed as performing well with diesel and biodiesel blend fuels and other petroleum products.

Do the sizes follow AS568 standards?
The product is designed to meet AS568 size standards with nominal and actual dimensions provided for verification.

What temperature range can these O-rings handle?
They are rated from -26C (-15F) up to 232C (450F), suitable for many high-temperature sealing tasks.