The Aluminum MRT Bolt for the Invert Mini marker is only 9.0 Grams. Lightening the bolt means that the marker will naturally have less kick/recoil and take less pressure and time to move the bolt back and forth. This means your marker will produce less vibration and recoil with each shot. This in turn allows you to stay on target better... hence shoot more of your opponents. The Aluminum MRT Gold Bolt is hard anodized for durability and teflon coated for minimal drag and friction.