In a nutshell, when you buy the Umarex T.A.C. Converter XBG CO2 BB Pistol Combo, you get the XBG CO2 4.5mm BB Pistol preinstalled in the T.A.C Converter, you also get the included fore-grip which is renovable by the way can coudl be used stand alone on any other gun with an under barrel Picatinny rail. Read full article here: https://www.replicaairguns.com/2014/10/4/umarex-tac-converter-xbg-co2-bb-pistol-combo-full-review.html Buy the T.A.C. Converter XBG Combo in Canada: http://www.replicaairguns.ca/umarex-tactical-adjustable-carbine-co2-pistol.html Buy the T.A.C. Converter XBG Combo in the US: https://www.replicaairguns.us/umarex-tactical-adjustable-carbine-co2-pistol