"Great battery, Fits in my EMG SAI GRY Salient Arms buffer tube. (Its an M4.) But every gun is different. I will say it is surprisingly small for the Mah that it has. Lasts me all day in serious game play.
"Overall, great battery. Personally, I made the mistake of buying this for a rifle that was too small for it, but to give the product a review, I took off my stock. Be aware: this battery is huge: i recommend that if you do plan on using this for an M4, you are going to have to accept adjusting your stock all the way backwards. Well with that out of the way, the battery comes in a rubbery plastic bag with a zipper on the top, so nothing special, or even a manual. (Potential con). However, in regards to performance, it easily won a 5 star review. Just to test the quality of the battery, I had fully drained it, charged for 5 mins and threw it in my ICS CXP-APE. It ran for a good half an hour on semi, and being as though I only charged it for 5 minutes, this is impressive. The fully charged battery lasted (and we ran a 7000 round custom electric magazine) on fully auto , and it took 5 magazines (yes,that's 35000 rounds) wbefore it died. I'd also like to mention that we were doing a gun meltdown and neither faltered, which was ridiculous. So, if you do plan on buying this battery, I would recommend a big buffer tube. Overall, great buy.