Does anybody own an Ultrafire 501B and the Sipik CK361 Recoil?

I only ask because I think I heard that the tailcaps are interchangeable and would like to confirm this.

Don't know about Sipik, but 501B and UltraFire WF-008 recoil have intercangeable tailcaps. Sipik is probably internally the same as WF-008, so I guess the tailcaps are interchangeable.

Sounds promising.

Thank you.