Extended Top Rail with 17 Slots for Flexible Eye Relief Adjustment, 2 Removable Side Rails with 12 Slots for Additional Accessories * Features Innovative Double Locking System with Zero-Gap Tight Tolerance for Most Secure Fit * Great Zero Retention Capability for All Accessories Installed on the Rails * Includes 2 Steel Adaptors to Replace Rear Sight for Dual Use on Either Full Size or Carbine Rifles * Intensively Tested by Field Experts and Demonstrates Most Satisfactory Performance, Friendly Installation, No Gunsmithing Required