My guess is you are using a Surefire host. LED durability is good. I'm not even sure you'd need the spring but to be safe, and if it's just a 6P, buy a Solarforce host and forward clicky switch and you should be able to use the drop in as is. I've used dropins with my Z2 with great success but takes more tweaking to get reliable function. Therefore I'd just go with the Malkoff or Over Ready drop ins with Surefire and use Solarforce with the cheaper drop ins. The newer Solarforce, check with your distributer, L2m can be used as a single 16340 size host or as a single 18650/17670 host. It's already bored to fit the largest 18650s. (Check your drop in distributor for dropin voltage limitations.