CDHPOWER Bicycle Gas Frame 3.4L For 2-Stroke & 4-Stroke Engines. Requirement on switch of gas frame: 10*1.5mmrear width:126mm Requirement on headset size:1 1/8"; bottom bracket 1.732" /44mm diameter;Requirement on seatpost:27.2mm; the width and Inner Diameter(including depth of screw) of the bottom bracket:68mmx35.4mm/2.677inx1.3937in Gas Tank Cap included; For gas motorized bicycle only Diameter of downtube:42mm; Requirement on seatpost:27.2mm PLEASE NOTE 1: the best safe speed if racing: 35km/hIf buyers' bike rear wheel is with quick release,we suggest buyers do not buy the gas frame unless buyers are professional. Any questions,please contact us firstly! we can help you solve the problem until you are satisfied.