Spa-Tech temperature sensor used on imported spas from Oasis Leisure Products & Others.

PLEASE DOUBLE CHECK THREAD SIZE. DON'T RELY ON WHETHER IT'S PLASTIC OR STAINLESS STEEL. They used both Stainless Steel & Plastic types, but the thread size is the important part, not the appearance. 

There are two versions of the temperature sensor:

• New style with chunkier nut and thread - has a 9.5mm diameter thread. It can either be the large-nut Stainless Steel, or Black Plastic with Gland style. (interchangeable). This Sensor underwent a change late 2018 to a plastic nut / SS thermowell. 
• Old style has smaller nut and thread - has 7.7mm diameter thread. These are no longer available.