This adjustment spacer allows for precise height modification of Rega tonearms from 0.5 mm to 3.5 mm in 0.5 mm increments, facilitating the proper setup of Ortofon cartridges with lower-than-standard mounting height; 3.2-4 mm spacers are recommended for Quintet cartridges. Simply loosen the tonearm screws, insert the spacer, and secure the screws without the need to remove the tonearm.