This is a package of 50 gaskets for threaded keg valves.
Threaded valve gaskets come in two styles based upon the design of the valve. Most Micromatic valves utilize a security latch mechanism within the valve to prevent consumer tampering. This type of safety lock requires a specific tool be used to remove the valve from the keg neck. Observe the top edge of the valve body and notice that there are two notches or lugs that the removal tool fits over.
Look closely at the inset photo for the letter S on the left lug and examine the lugs for an engraved letter S. You may also find the letter R or possibly no engraving at all.
If you have a letter S on one of the lugs, then order the super-lock gaskets.
If you have a letter R or no marking, order the regular gaskets.