This sight has adjustable yardage markers built into the sight where you would normally place a piece of paper and mark yardages with a pen.  

Once you have determined the desired yardage, simply move the yardage marker to its proper location and tighten a cap screw.  

There are three markers included with each sight and you can add more for longer yardages if desired.  The sight also features a dual track slide system which reduces unwanted play found in most sights.