I made some focus sticks for my galvo laser. 

They require (2) M3 x 8 screws, (2) M3 washers, and (2) M3 square nuts.

There are also 1-3mm offsets for Z engraving

I printed the stick body with the channel facing the bed with tree supports. 

Range: 

50mm (50-80mm)

80mm (80-120mm)

120mm (120-200mm)

150mm (150-260mm)

200mm (200-360mm)

250mm (250-460mm)