This is a .225 high front sight RAMP manufactured by Marble Arms here in the US. This ramp is precision milled from solid steel and comes with the attachment screw (6-48 thread). The machine cut grooves on the surface of the ramp decrease reflections that can diminish accuracy. It is for rifles with a 11/16 inch (.6875 inch) diameter ROUND barrel. You will want to use the RAMP STYLE front sight that is .340 inches in diameter to fit into the 3/8 inch dovetail milled into the ramp. A few examples of sights that you could use with this ramp are st5, st6 st28 st29.