CST - Center String Technology - PXL Capture Aperture located on center of bowstring - no L and R misses. OCT - Optical Centered Technology - Improved centration of lenses for ultimate accuracy. PLT - Protected Lens Technology - Lenses protected by plastic on 2 sides prevents cracking. DSAT - Dual String Angle Technology - has both 37 and 45-degree string angles on the same peep housing. TAP - Tool-less Aperture Technology - Knurled Tool-less PXL Capture Aperture - eliminates the need for an aperture wrench. PXL Clarifier or Verifier lenses can be removed from the Capture Aperture for easy cleaning. Additional "PXL Hunter Peep Shade Cap" accessory - screws into front of peep to prevent glare. NOTE: PXL Hunter Peep Apertures fit into Specialty Archery PXL Hunter Peep ONLY. NOT compatible with other Specialty Archery peeps.