Technical Specifications Set Contains Mag Base With Microfine Adjustment Screw, 3-9/16 Extension Arm, Dovetail Mounting Kit Contains: Mag Base With Microfine Adjustment Screw, 3-9/16 Extension Arm, Dovetail Mounting - Xtra Mag Magnetic Base 52-585-105

Technical Specifications Set Contains Mag Base With Microfine Adjustment Screw, 3-9/16 Extension Arm, Dovetail Mounting Type Xtra Mag Magnetic Base Brand Name Fowler ”2 universal ball sockets ”Microfine adjustment screw ”3" extension arm ”Dovetail mounting ”Range: .030" ”Reading: 0-15-0 ”Jewelled movement ”Graduation: .0005" ”Auto-reversing ”.080" diameter point.