CDHPOWER Bicycle Gas Frame 3.4L For 2-Stroke & 4-Stroke Engines. Requirement on switch of gas frame: 10*1.5mmRequirement on headset size:1 1/8"; bottom bracket 1.732" /44mm diameter;Requirement on seatpost:27.2mmGas Tank Cap included; For gas motorized bicycle onlyDiameter of downtube:42mm; Requirement on seatpost:27.2mmrear width:126mm,head tube length 150 mmthe width and Inner Diameter (including depth of screw) of the bottom bracket : 68mmx35.4mm/2.677inx1.3937in 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 braketriple tree suspension fork is compatible with our gas tank frames.26" front fork: suspension with double shoulder;Disc brake bracket and U caliper bracket;compatible with 26"*2.325 inch tire maxHeadset is 1 1/8'' and works well with the fork Outside Diameter of Up Tube:2.89cm/1.138inch and 38.1mm/1.5 inch for lower leg, Suspension forks does not work well with Bicycle handle bar which fits well on out leg diameter 3.15cm to 3.18cm(1.24inch to 1.25inch) of triple tree fork Please clean the black color painting on thread of bottom bracket before you assemble the crankset.This combo include 1pc 3.4L frame, 1pc Non-suspension fork, 1pc 1 1/8 headset