These two tools are used to release pressure in hydraulic systems with quick couplers. They should work with Pioneer, Ag, or ISO B couplers. Both male and female versions are provided. You basically insert the approriate tool into the pressure locked fitting, and then turn the screw knob until it breaks the pressure.

The knob is M6 x 30mm and the items are printed from PETG in order to get some oil resistence. The slip ring holder is just glued to the body to hold the slip ring in place.