Generac 0C8646 Belt Tensioner Pulley 4.5" Flat QP-75D.
For entire replacement tensioner kit with pulley, arm, and hardware, see here:
Generac 0C86440SRV Belt Tensioner Kit With Arm & Pulley/Hardware QP-75D
Generac replacement parts will also usually fit the following Generac branded generators: Honeywell, Guardian, Siemens, Carrier, Watchdog, Centurion, Eaton & Bryant.
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