This hot tub pressure switch comes branded either Tecmark (3902 or 3903 with screws) or Hydroquip 34-0178, they are exactly the same switch just labelled differently.

Height: 58mm
Width: 50mm
Connections: 1/8" MPT screw thread (connection to heater) / 2 x flat spades (connection to contact wire)

Used  in Gecko, Hydroquip, CTI & Spa Builders  control boxes.

A variety of spas including Beachcomber, Arctic Spa, Artesian Spas, Coyote Spa, Dimension One, Gulf Coast, Hydrospa, Hotspot, Inspirations, LA Spas, Sierra Spas, Southwest Spas, Sunrise amongst others

The unit is extremely easy to replace, but be aware when refitting it is advisable to drain the spa to prevent water damage through spraying onto the circuit board as this pressure switch is normally found inside the control pack.

It has a PSI gauge on the side but we do not (usually) recommend adjusting this, however if you decide to then do it gradually.

Older models that can be replaced by this switch are smaller, red and black underneath.