Rotor Alignment is very IMPORTANT! Follow the pictures carefully!

Make sure there are sharpie marks on the side of the Rotors where it lines up with "T" and "B" on the rotors

Align the Side Mark of "T" Rotor to the "T" on the Housing, and only insert Top Rotor into the housing.

Align the Side Mark of "B" Rotor to the "B" on the Housing, and insert the Bottom Rotor

When aligned properly all 8 holes made by 2 rotors intersecting should have equal spacing

Verify that you can manually turn the eccentric shaft in the center and that the rotors smoothly turn inside the housing. Tight printing and misaligned rotors can cause the gearbox to jam.