I've watched a few youtube videos on buffer kits. My understanding is that the finish on the inside needs to be smooth to keep your bolt from excessive wear. It said that commercial tubes have a slightly bigger outside dia. than milspec. Is the ID the same though? I really don't care what type of stock I'm able to find right now. I just want the gun to function properly w/o doing excessive wear on anything. I'm also thinking the tube should have a the proper class of threads that will thread into my receiver nicely. I don't want any problems at that point. So I'm almost automatically not wanting to expermint with any not proven stuff. I also am not sure if the buffer weight or length has anything to do w/ the length of the upper or rifle? Selection is scarce, and I'm probaly going to have to pay hard for this, so I want to get the right one the first time. I supposedly getting a complete RRA 0550 20" varmint upper for my MP 15 stripped lower. I just ordered a 155.00 dollar DPMS parts kit. Now I believe all I need is a buffer kit? Being I've said what parts I'm working w/, I'm hoping some people will give me some advice on what tube, spring, weight, or stock,buffer nuts, to look for or ones to stay away from. I've been on gun broker and ebay, the selection is so poor, that I may have to piece together something to work from several differnet sources. Any advice would be appreciated. I've got longer arms than average, and my near sightness gives me blurry vision on rear sight, so I like to sit back from the gun as much as possible. I mention this only because I'm not sure if theres options on length of tube. Most Importantly, this thing needs to function properly and a reliable as possible.