8400 SERIES BUNA CUP 3-1/2 X 4 X 1/4W

Buna-N/Nitrile/NBR 8400 Series U-cup seal, item NU8408-0350, for hydraulic cylinder, pneumatic cylinder, rod sealing, and piston sealing applications. This cup-style profile uses a flexible sealing lip to help control fluid bypass while supporting smooth reciprocating motion. The product is listed with nominal dimensions of 3 1/2 inch ID x 4 inch OD x 1/4 inch height and actual dimensions of 3.5 inch (88.9 mm) ID x 4 inch (101.6 mm) OD x 0.25 inch (6.35 mm) cross-section/height, helping buyers compare the seal to equipment drawings, gland dimensions, or removed parts during maintenance. Buna-N, also known as nitrile or NBR, is a common sealing material for industrial service where resistance to petroleum-based oils and general hydraulic fluids is required. Series references such as 8400 Series or 6226 Style are retained when they appear because they help identify the correct cup seal family. This product supports common buying terms such as hydraulic U-cup, Buna-N U-cup seal, NBR cup seal, rod seal, piston seal, and replacement cylinder seal. Item NU8408-0350 is included for SKU-level identification in equipment records, drawings, maintenance lists, and reseller product catalogs.