Zippe-type centrifuge "...Pakistan's nuclear program developed the P1 and P2 centrifuges -- the first two centrifuges that Pakistan deployed in large numbers. The P1 centrifuge uses an aluminum rotor, and the P2 centrifuge uses a maraging steel rotor, which is stronger, spins faster, and therefore enriches more uranium per machine than the P1 centrifuge's aluminum rotor...."
Reference: en.wikipedia.org .