GM "Performance Parts" model number gm2813. Its an 1/2" and will come with 13mm-22mm plus a 10mm and a extension part. Here is some info on the box: 2100 RPM No-load, 2,7000 impacts per minute. The motor delivers up to 240 ft./lbs, seemed to work just fine for everything I used it for. The main reason why I'm selling this thing is because I'm moving back home to pursue my Army Chaplin career and with the price of gas...psh. I have only used this for one day and my moving date change so its a tad earlier. It requires a lot less room then an air impact because you don't need an air compressor.