Is there different size buffers ? I ordered a complete mil-spec buffer tube assembly and it came with a buffer, just wanted to make sure this is the right size. This is on a CTR mil-spec stock.

If it came as a kit it should be the right one.  About 3 1/4" long.  They don't come in commercial or mil spec sizes if that is what you are asking.  Basically there is a carbine buffer and a rifle buffer.  The rifle is obviously longer than the carbine.

There are different weights of carbine buffers, but I don't think that is what you are asking.

Mil Spec and commercial only refers to the carbine extension (tube) and the stock itself, not the buffer, spring, castle nut or retainer plate.  Those are the same for either.

So as long as your buffer is not over 3 1/4" you are good.  Hopefully that answers what you are asking without too much confusion.

Thank you for that info. That is what I was looking for