Picatinny cross-section aluminum rail stock gives you a head start on building custom scope bases. Pre-contoured, so you need only cut to required length, mill cross-slots, radius the underside (if needed), and drill mounting holes. Much easier than machining from scratch from bar stock. Perfect for installations that require special ring positioning. Place cross-slots only where you need them; dovetail contour accepts Picatinny or Weaver-style rings. Channel down the center keeps weight to a minimum without compromising rigidity.