the single piece 66cc can be tapped out to 8mm for using aftermarket jugs. it originally comes with 6mm SHCS for jug/head bolts. or if you are not mechanically incline with tools, you can install a 8mm od x 6mm id steel sleeve/tube and just use some m6 all thread rod. when making the tube, make sure it does not go all the way through the head holes. to allow for head expansion. if you make the sleeves to long, you will blow gaskets every time the motor gets hot.