Heavy Duty Automatic Changeover LPG Regulator connects to two propane tanks and automatically changes from empty to full unit without service interruption. The unit will Red FLAG the empty tank indicating refilling is needed. 450,000 Btu output is perfect for multiple appliances of a standard size home. 1/4″ inverted flare input wi/ 1/2 NPT output. Use with RP-24″ Pigtails. Needs 2 pieces. One per tank hook-up.