Forward Control Design's ASF was designed to be a defense, duty or combat safety selector. That being indicated by the way its levers are attached at the center by a stainless steel roll pin. One of the design goals was that there would not be any wobble between the lever and the center with the tight tolerances on the ASF's lever and center interface to accomplish that. 

The Q levers are offset levers with the lever sitting closer to the shooter's thumb when the selector is on "FIRE", allowing the user to easily rotate it back to SAFE without needing to change their grip. Q levers are specific to a side. The Q lever's "leg" should always be biased towards the top. With the selector in the FIRE position, the Q lever should look like the letter q. 

The ASF's profile isn't squared with its most outer portion being tapered, conforming to the shooter's thumb pad when holding the pistol grip. 

The end cap is for the individuals who wish to not have a lever on the weak side of the receiver. With the end cap installed, the ASF becomes a convertible selector (between ambidextrous and non-ambidextrous) giving the shooter the ability to run the levers on either side and either length for the ultimate comfort fit for their style of shooting. 
 
ASF's centers are machined in 8620, heat treated and black nitrided. The levers are machined in 8620 and black nitrided.