Naraku Variator Control Shims for QMB139 50cc engines. Variator control shims can be installed between the drive faces to lengthen the boss if your variator does not open fully to allow maximum belt travel. For use with 20mm variator bosses only! Includes 10 shims of each size: .1mm, .2mm and .5mm. Also fits stock variators on fits and compatible with Honda Ruckus and Metropolitan and 2-stroke fits and compatible with Honda Elite SA/SR 50, Kymco ZX50/Super 8/Super 9, and SYM DD50. Please see our Warranty & Returns Policy.