Weber sells Genesis knob sets (2011–2016) for $47.99 and Spirit pairs for $29.99 — and sun-baked grill knobs crack constantly. Print replacements in UV-tolerant PETG, sized to your valve stems, for about $20 shipped.
Shaft fit: D-shaft valve stems — pull a knob and measure; grill valves are commonly 8mm class but vary by generation. Knobulator lets you set the exact bore
shape and clearance, so the knob grips the shaft instead of spinning — the usual failure of
one-size-fits-all replacements.