Rennline’s billet aluminum heater control knobs are the perfect inexpensive interior upgrade for any 911/914. Factory heater control knobs become faded, cracked, and/or unsightly after years of exposure to UV light. Rennline billet knobs are machined from 6061 aluminum and are available in red or black anodized finishes for a durable, long lasting appearance. Simply pull off your old knob, and tap ours on, installation is literally a snap.