I just peeled the coating off of an UltraFire 18650 3000mah battery in my GGTS. I started to insert one and it seemed tight. I thought that one may have swollen some and i tried a second one. It went in snugly but then wouldn't slide down all the way, so I decided to remove it. When I did it peeled about an inch of the insulation off of the bottom 1/4 of the battery. The TrustFire 18650 2400mah fit fine, I guess the red 3000mah are a little bit wider. It is possible all UtraFires are a little wider, I only have the 3000mah version.
Since this thread is for the battery compatibility of all GGs, I should probably note that these batteries work great in the GGT and last for a very long time!
I also have the Ultra-Fire 18650 3000mah batts. is it okay for the protection strip to come into contact with the inside of the GGTS? It is a tight fit, and the outer skin on the battery is getting pretty messed up. Can I just peel the skin off of the battery and use it without the skin?