Here is the very popular 3037P Spa Pressure Switch manufactured by Tecmark-Tridelta. The "P" stands for Plastic, as the switch has plastic threads.
Tech Note: When intalling any pressure switch, always remember to wrap 3-4 layers of teflon tape around the threads, to ensure a good seal. We have included a Free Roll of Teflon Tape with your purchase. Feel free to contact us with any questions.