The Pro-Ject 52g counterweight is a genuine spare and upgrade part for Pro-Ject tonearms built around the 081 tonearm assembly, which uses a 10mm stub diameter rather than the more common 8.6mm stub found on older Pro-Ject arms. A counterweight must be correctly matched to the cartridge being used: if a cartridge is too heavy for the standard counterweight to balance properly, it cannot apply accurate tracking force, leading to degraded sound quality and potential stylus or record damage.
Replacing the standard counterweight with this 52g version allows the correct cartridge weight range to be balanced within the tonearm's recommended tracking force range. The counterweight fits directly onto the tonearm stub and locks into position with a grub screw; tracking force is then set by sliding the counterweight along the stub in the usual way.
If you are replacing a lost or damaged counterweight, or upgrading to a cartridge that falls outside the range of your existing weight, confirm your tonearm uses the 081 assembly with a 10mm stub before ordering.