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.
The 2 inch Pump Split Nut is used as a replacement for the pump union that would need to be re-plumbed. You can cut off the old pump union and replace with this split nut. This comes with the 2 screws that screw and hold it together.