Perfect for the k versions or regular versions of the apc and ghm - A3 Industries Modular Vertical Foregrip For B&T APC-K

The ten degree forward angle of the grip is comfortable on the wrist. The knurling on the handle is just right. Think carefully about the thickness and length of your fingers, and the width of your hand before you decide which handle to get--or whether any of them will be a good fit for you. I bought the 2.5" handle because it's the thickest, and I have long fingers. I should have gotten the 3" handle because my hands are wide. (I wear XL gloves.) If you have thick fingers, you may wish you had more room between the handle and finger guard.
This item was sized to fit the "K" versions of the B&T GHM and APC9 models, but I bought it for a standard size APC9 Pro, and the only trade-off I can imagine is the reduced distance between the handle and finger-guard, if you have thick fingers. The compact size conserves space on the 6 o'clock rail, leaving two grooves open (maybe three if you position it all the way fore or aft). The fit on the rail is very snug and precise. The rest of the workmanship is precise. The hardware that bolts the base to the rail is beautifully designed and made. Beware the design of the handle, though. It threads on to a bolt, and it comes loose even when you're just holding the weapon--this is a serious problem. There's enough room inside the handle to fit a washer and nut, which will probably solve the problem. I'd do that before I'd put adhesive on the threads or mating surfaces between the handle and base, but I guess that could work, too. I subtracted one star because of that.