The pressure switch in your spa controls the water pressure in your spa. The pressure switch harness is a replacement part for the original pressure switch harness that allows the pressure switch to be connected to the controls of your spa.
The Drain Plug for Power WOW is a wet end drain plug for the Pentair Power WOW. This part does not come with an O-ring. The part allows the pump to be drained of stagnant water so protect it from damage and to keep it running for as long as possible.
The pressure switch - MAS400 - is specifically designed to replace the original pressure switches in the Legend Series Master Spas 2000 CS models. Control the water pressure in your spa with the right part.