We strongly recommend the X-Ring for most purposes:- Here is some info towards help you selecting your chain:-
Compared with Normal O-Ring, X Ring has:-
Half the Power Loss
1.5 to 2 Times Longer Wear Resistance
D.I.D’s PATENTED X-Ring construction reduces friction by twisting between the side plates instead of being squashed. Normal O-Rings and other makers’ modified O-Rings have squashed points that increase friction. The twisting action of the X-Ring disperses the pressure and minimizes power loss. X-Ring is a U.S.A. Registered Trademark of D.I.D; Daido Kogyo Co. Ltd. Japan
The X-Ring’s four contact points greatly increase its sealing performance. This keeps the dirt out and the lubrication in much better than any other O-Ring. X-Rings have the greatest wear resistance of any other type of O-Ring or Non-O-Ring chain.