Rega Heavy Tungsten Tonearm Counterweight 120g, for heavier cartridges.
If you’re putting big MC cartridge in the 10 gram+ range you should put this heavier tungsten counterweight on your Rega tonearm.
For cartridges less than 10g, which is the vast majority of cartridges you use on a Rega, use the lighter 100g tungsten. The 100g tungsten is the one you want if your goal is to allow you to close the Rega turntable lid after raising the tonearm pillar (done for non-Rega Cartridges).
This is compatible with Rega tonearms that do not have screw-on counterweights. For turntables this is the Planar 3, Planar 6, and Planar 8.
For current models tonearms, the RB220, RB330 and RB880.