The top sight lines up with the BT raise sight rail. Featuring cool looks and easy installation, the BT-16 is a great barrel mod for those searching for the distinct M-16 look and feel. <br> <br> The BT Apex barrel has on/off capability and an adjustable ramp switch that allows you to choose the desired level of curve. Simply twist the barrel to deliver shots that hook left, right, drop, or maintain a long, flat trajectory. The Apex dramatically increases your available shooting angles and can quickly be adjusted during the heat of the battle. Another great feature of the Apex is that it is easy to clean.