Advantages of X-Rings vs. O-Rings
 
Prevents contorting in the groove. The seal is not apt to roll in the groove with corresponding movement.
Low friction. It requires less radial squeeze compared to a standard o-ring.
Less wear due to low friction, thus providing a longer service life.
Excellent sealing efficiency with its special profile.
Improved startup with the lubricant reservoir formed between the sealing lips.