Mutual Screw & Supply

0.21" CS X 18.975" ID Viton FKM O-Rings | AS568-391 | Dash 391 | 75 Durometer | Black (2 / Pkg.)

0.21" CS X 18.975" ID Viton FKM O-Rings | AS568-391 | Dash 391 | 75 Durometer | - Main image
$33.42 $53.91 In stock

Viton FKM o-rings in AS568-391, 18.975" inner diameter by 0.21" cross-section. Service range -15°F to +400°F (-26°C to +204°C). Also known as FKM, Fluoroelastomer.

Specifications

  • Product type: O-Ring
  • Material: Viton FKM
  • AS568 dash size: 391
  • Cross-section: 0.21" (5.33 mm)
  • Inner diameter: 18.975" (481.97 mm)
  • Durometer: 75 Shore A
  • Color: Black
  • Temperature range: -15°F to +400°F (-26°C to +204°C)
  • Measurement type: Imperial
  • Pack quantity: 2 per package
Before you pay

Check the method and total at checkout.

When it ships

Allow for processing time as well as the journey to you.

Standard Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

Express Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

View policy
If you need a refund

Keep your order number and contact the store to start.

Please contact us for the refund processing timeframe before returning an item.

View policy
Delivery costs

Review the cost for your destination and chosen service.

Standard Shipping · United States: $0.00

Express Shipping · United States: $3.99

View policy
Returning an item

Check the return conditions before sending anything back.

United States · Return window (days after delivery): 30. Return method: By mail. Return postage: Seller pays.

View policy

Customer Reviews (4.8 / 5 · 5 reviews)

Robert U. ★★★★★

Used these to replace the worn seals on my old clamp setup and the 75 durometer hardness feels just right under pressure. The Viton material handled the heat cycle to 400°F without any visible swelling or cracking. Exactly the standard AS568-391 size I needed, and the two-pack gave me a spare for ne

Ellie O. ★★★★★

The 75 durometer hardness is spot-on for my application—it held its shape perfectly under compression. Fit the groove exactly as the 18.975" ID spec promised, and the black Viton handled the heat without any visible warping.

Christopher N. ★★★★★

I needed a high-temp seal for a vacuum chamber port that sees steam cycles, and these dropped right into the groove without any trimming. The 75 durometer feels firm enough to hold a solid seal yet still pliable during installation. Worked perfectly on the first test after reaching 350°F.