I am considering a light for my Glock 17 Generation 4. Lots of options. I like the Streamlight TLR versions. I'm confused about the options offered. Some have these little finger grips (like a wing nut) on what I think is the battery compartment. There are multiple mounting versions. Can someone tell me exactly what I should get? I don't really care about the strobe light setting. Are these rechargeable? Thanks for your help.