These weights mount on to the exterior of any chassis or stock that is M-Lok compatible. They mount using standard hardware and M-LOK T-nuts, meaning that you can install and remove them as necessary on your system. A pair of weights and hardware will add 0.78 lb/354 grams to your chassis/stock.
The interior forend weights can be added and removed without removing your barreled action, simply remove the forend cap, slide them into the desired location under the barrel, and screw them in place from the bottom.
The M-Lok forends for the TAC21 provide an integral accessory mounting system without the need to first attach a picatinny rail. The M-Lok forends come in the standard 11” length and a new 15” length, providing an additional forend length option.