Case-hardened steel; Underside clearance slot to allow mounting of M-LOK accessories to ACC Chassis forend even with weights installed; Side clearance slots to allow mounting of M-LOK accessories to ACC Chassis forend even with weights installed; 3 sets of mounting holes to allow the weight to be shifted inside the barrel channel at 20mm (3/4") increments for tuning the rifle's balance point; Hardware Included: Four #10-24 x 1/2" Flat Head Cap Screws per weight for fastening to the chassis; Weight: 0.52 lbs / weight (including screws); 5-Pack: 2.60 total weight