The Improved Tang Sight's quick-release post system makes it easy to replace the post that came with your sight with a higher or lower one for targeting at different ranges.Choose a lower post for close-in targets or a taller post for longer ranges. Post height is also click adjustable for fine-tuning when sighting in; each click represents A 1/4" of adjustment at 100 yards. A jam nut locks the elevation, so you can remove and reinstall a post without losing settings. Mfg: Marble Arms SPECS: Steel, blued. Heights measured from base of post to center of aperture. Medium - 1.875" to 2.965" height adjustment range. A 3/4" aperture disc with .032" peep.