Thumbscrew 1/4 - 20 x 1.75 inch. These are used to secure your corner skirting pieces on your spa in place. This part is the longer of the two thumb-screws available.
A spa circuit board is the "brains" behind your spa, controlling jet flow, filtration systems, water temperature, as well as the unit's high-limit sensors. Master Spa Parts offers a number of replacement circuit boards.