This is a ADCO Mag Loader/Unloader known as the Super Thumb model ST1PR.
This choice is great basis for pistol shooters who want a light weight 3.9 oz sight on their hunting or target pistol. 1 inch rings. Red or green with a 3 MOA dot size give the shooter the means of taking fast and accurate shots after sighting in as they would any other optical sight system. Eye relief is not important as this is compatible for pistol or rifle shooting.