Loaded U-Cup

Loaded U-Cups derive their name from their "U" shape and the elastomeric energizer they use to provide more effective low pressure sealing.

U Cups seal on both the inside outside diameters
U Cup seals are often used for piston or rod seals due to the small gland space required
U Cups are usually specified in low speed, low pressure environments 
U Cups seal by means of the flared, flexible lip in contact with the rod or cylinder wall
      
Dynamic contact surfaces should have a finish of 8 - 16 RMS.