Ryobi 720R Carb and choke plate trimmer part only | eBay
791-153066B Bump Head Knob Assembly Replacement for Ryobi 720r (41AD720A034) Handheld Trimmer - Compatible with 791-153066 Right Hand Bump Head Knob - Walmart.com
Page 17 of Ryobi Trimmer 720r User Guide | ManualsOnline.com