ARMS products are great. I dont own one, but they have a rock steady reputation here. The 40 and 40L are great BUIS. You will be able to easily use them as your primary sights until you get the ACOG and they will be just as accurate as a carry handle mount. For DCM matches you would want an A2 carry handle, but you tactical courses will be well served by the 40 series. Most people dont like the ARMS 40 A (I think) that has the small ring notched on top. This clears the ACOG, but people say it distorts their sight picture. The 40L is the best of everything for only a few bucks more. The only complaint is it resets to the small aperature, but if you always have it up as a primary sight you can just keep the large aperature up. If you have an ACOG and the sight is down, it wont matter. Only if your scope fails and your taking it off in the heat of battle will the 40L's resetting to the small retical affect you.