CDHPOWER Bicycle Gas Frame 3.4L For 2-Stroke & 4-Stroke Engines. Requirement on switch of gas frame: 10*1.5mm；Requirement on headset size:1 1/8"; bottom bracket 1.732" /44mm diameter;Requirement on seatpost:27.2mm; Gas Tank Cap included; For gas motorized bicycle only; Diameter of downtube:42mm; Requirement on seatpost:27.2mm; rear width:126mm,head tube length 150 mm; the width and Inner Diameter (including depth of screw) of the bottom bracket : 68mmx35.4mm/2.677inx1.3937in >br>Bottom bracket: 35.4mm (inner diameter)&44mm (outer diameter);PLEASE NOTE 1: the best safe speed if racing: 35km/h；If buyers' bike rear wheel is with quick release,we suggest buyers do not buy the gas frame unless buyers are professional;Rear brake:Disc brake This Combo include 1pc 3.4L silver frame, 1pc 1 1/8 headset, 1pc silver motor mount, 1pc tank valve 10*1.5mm