Modular riser mount clamps to a flattop Picatinny receiver, so you can mount a scope at correct eye level for maximum accuracy. The separate base has two, oversized, easy-grip thumbscrews and full-contact clamping along entire length of base to provide rock-solid attachment to receiver without permanent modification of gun. This mounting system will not shoot loose no matter how many rounds you send downrange. Risers are sold separately, so you can choose one with the precise rail height and angle to suit your needs; riser is secured to base with three Allen head setscrews. Use an angled riser when you need to raise or lower the point of impact more than the scope's internal elevati Mfg: Brownells SPECS: Precision machined 6061 T6 aluminum, hardcoat anodized matte black. Base is 1" (2.5cm) wide, .3" (7.62mm) high. Available riser heights (including base): ¾" (1.9cm), 1" (2.5cm), 1¼" (3.2cm). Base and risers sold separately.