Rheem RTG20213D MIC-Q-18 18FT Manifold Control CableAll indoor tankless gas water heaters must be vented vertically or horizontally to the outdoors using factory approved venting material (No other venting material is permitted). See the Use and Care Manual for important information regarding the venting installation and materials for your tankless water heater. NOTE: Rheem outdoor tankless water heaters do not require venting materials. Rheem RTG20213D MIC-Q-18 18FT Manifold Control Cable Features:Manifold Control Cables (Type Q) One required for each tankless water heater installed in a manifold. Connects a single tankless water heater to the MIC-6. Note: These cables will not fit the MIC-180. Model: RTG20213-D Rheem offers many venting accessories to make your tankless water heater installation easy.