Integration means stability. Browning’s Integrated Scope Mount System unitizes the ring and base into a single ultra-rigid unit. Machined from 7000 series aluminum alloy they eliminate alignment problems and the possibility of a loose connection between the base and ring. They are available in .400 Standard height .500 Intermediate height and .600 High height versions to fit your needs. Machined from 7000 series aluminum for high strength and durability The integrated design eliminates alignment problems and the possibility of a loose connection between bases and rings .400 Standard height .500 Intermediate height .600 High height Important: These fit the AB3 only. They do not fit original A-Bolts or A-Bolt II receivers.