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Black Buna-N O-ring, 3-3/4 inch inside diameter, quarter-inch cross-section, pack of five

Zoro Select

Zoro Select O-Ring 3-3/4 in 1/4 in Buna-N Black PK5

SKU CH-KWD6-JNX9E

Pack of five Buna-N O-rings with 3.7 in inside diameter, 0.275 in cross-section, rated from -40 to 250 °F and FDA approved

  • Medium-hard 70A durometer resists extrusion
  • Buna-N handles -40 °F to 250 °F range
  • FDA-approved material suits food-contact uses
  • Metal-detectable design aids contamination control
  • Pack of five covers multiple sealing points

O-Ring 3-3/4 in Buna-N PK5

This pack contains five black O-rings made from Buna-N rubber with a 70A durometer hardness. They suit maintenance, repair and assembly tasks where a medium-hard seal is required. The material is FDA approved for incidental contact. Buyers needing X-ray detectable seals or different elastomer chemistry should look elsewhere.

Inch standard dash 419 dimensions

The rings follow the inch measurement system with dash number 419. Nominal inside diameter is 3 3/4 in and nominal width is 1/4 in. Actual inside diameter measures 3.7 in and actual width measures .275 in. Actual outside diameter is 4.275 in. These tolerances define the sealing interface.

Temperature range -40 to 250 F

Continuous operating range spans -40 degrees to 250 degrees Fahrenheit. Within this window the Buna-N compound retains sealing force and resists compression set. Beyond the upper limit the material hardens and loses elasticity. The pack of five provides spares for multi-point jobs or future replacements.

Highlights

  • Medium-hard 70A durometer resists extrusion
  • Buna-N handles -40 °F to 250 °F range
  • FDA-approved material suits food-contact uses
  • Metal-detectable design aids contamination control
  • Pack of five covers multiple sealing points

Specifications

BrandZORO SELECT

Questions about this item

Should I choose the 3-3/4 inch inside diameter or the 1/4 inch cross-section for my seal?

The 3.7 in actual inside diameter and .275 in actual width work together as one size — dash number 419 — so you order the single PK5 pack that matches both figures.

What does the 70A durometer mean once the O-ring is installed?

A 70A rating gives a medium-hard feel that resists extrusion under pressure while still conforming to gland surfaces in hydraulic or pneumatic systems.

How does the Buna-N material and -40 to 250 °F range limit the fluids I can seal?

Buna-N handles petroleum oils, water and many hydraulic fluids across that temperature span, but it is not suitable for ketones, ozone or strong oxidisers.

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