Typically the lightening holes are 1.150" by eight inches deep which the blower has to fill those twelve holes with precious horsepower making boost which the racer needs to be going down in the engine. These plugs are 1.160" by .870" long and the racer must tap them into the rotor then use the Teflon retention screw hole and drill into the teflon plug and tap it 6/32"' threads so the Teflon retention screw will help hold the Teflon plug in place.
Once this is done the racer must put the rotor in a lathe and face the Teflon plugs off flush with the end of the rotor. Plugs typically increase the boost level one to two pounds at the same blower overdrive. Plugs should fit all SSI sixty and hundred and twenty degree B, C, D,and F rotor blowers but smart to measure your rotors first just to be sure your lightening holes are about .005" smaller than 1.160".
Plugs are sold individual.