Finding the right counterweight depends on the turntable, the tonearm, and the cartridge fitted. Here are some of the most common Pro-Ject turntables and the counterweights they need. For reference, our most popular Ortofon cartridge weights are below. OM series: 2.5g 2M series: 7.2g Quintet series: 9g Cadenza series: 10.7g Counterweight #01 (75g) is suitable for the following Pro-Ject turntables:- Essential II, Essential III, Debut III, P1/1.2, 1Xpression AC (for cartridges weighing 6-9g)- Debut Carbon (for cartridges weighing 11g+) Counterweight #03 (95g) is suitable for the following Pro-Ject turntables:- P2.9 (for cartridges weighing 9-13g)- RPM 4, RPM 6, 2Xperience, P6.9, (for cartridges weighing 6-10g)- RPM 5, RPM 6.1 SB (for cartridges weighing 10-15g) [only for 2M Red version of the RPM5] Counterweight #08 (55g) is suitable for the following Pro-Ject turntables:- Essential II, Essential III, Debut III, P1.2 (for cartridges weighing 1.5-3g)- Debut Carbon (for cartridges weighing 6.5-8.5g)- 1Xpression AC (for cartridges weighing 3-5g) Counterweight #46 (83g) is suitable for the following Pro-Ject turntables:- RPM 5, RPM 9 Carbon, RPM 9.2 2 Xperience DC, 6 Perspex SB, Xtension 9 (for cartridges weighing 7-10g)- RPM 10 Carbon, RPM 10.1 Xtension 10 (for cartridges weighing 5-8g) Counterweight #80 (50g) is suitable for the following Pro-Ject turntables:- Debut Carbon (for cartridges weighing 4.5-6g)