These Hamamatsu Floating Frame Fixtures consist of a top float plate that will accommodate all 1.58 mm diameter tubes, a bottom float plate that will accommodate either a .229 mm, .457 mm or .787 mm diameter pin and 8 standoffs that keep the two plates separate. The length of the standoff is determined by the length of the pin used. For Hamamatsu pin tools we recommend the shorter FP_C series pins.