Maytronics Robotic Pool Cleaner Replacement Drive Pully Bearing Manufacturer Part # 3883645 Fits the Following Cleaners: Dolphin Nautilus Plus Dolphin Triton Plus Dolphin Nautilus Dolphin Triton Dolphin M200 Dolphin M400 Dolphin C5 Cb Dolphin C4 Cb Dolphin C3 Cb Dolphin Discovery Dolphin Saturn Pentair Prowler 820 Pentair Prowler 830 Dolphin Advantage Plus