I use this on the 4Sevens Maelstrom x7. It was designed for the quark lights in mind but works on the bigger bodied x7 great :) The finger grip allows you to hold the light with confidence that it will not slip out of your hand. Plus it allows you to still be able to use the hand holding the light. No need to hold light securely because you can just relax your hand. I would also consider getting the Leapers heavy duty lanyard.
Pros: High quality durable rubber, Can be used with any flashlight around 3/4"-1"
Cons: None
This review was written in the old system and had content requirements that are different than reviews written today.