This is the CMC Products 1911 .45 ACP 8 Round Match Grade Magazine with Pad.

The stainless steel match grade construction holds up to 8 rounds of .45 ACP ammunition. And no more guessing how many rounds are left – there are witness holes on the right and left side of the magazine. Its improved tolerance stainless steel USGI-style tube comes with enhanced feed lips. This CMC Products 1911 magazine is match grade, and features a welded baseplate for ultimate durability. This magazine has the optional, impact-resistant polymer baseplate.