U-cup depends upon contact made by its flexible lips. The solid section at the heel of the cup is generally narrower than the packing groove width and does not come into contact with the groove base and the adjacent part until pressure is applied. Consequently, when installed, the packing is slightly pre-loaded. U-cup packings have low frictional qualities and are completely automatic in action. Due to their design, they can be assembled satisfactorily in glands which have variations in cross sectional dimensions, thus permitting more liberal manufacturing tolerances. U-cups packings are also very successful in applications where it is desirable to reduce excessive packing friction.

U-cup depends upon contact made by its flexible lips. The solid section at the heel of the cup is generally narrower than the packing groove width and does not come into contact with the groove base and the adjacent part until pressure is applied. Consequently, when installed, the packing is slightly pre-loaded. U-cup packings have low frictional qualities and are completely automatic in action. Due to their design, they can be assembled satisfactorily in glands which have variations in cross sectional dimensions, thus permitting more liberal manufacturing tolerances. U-cups packings are also very successful in applications where it is desirable to reduce excessive packing friction.