Knob for the release valve on any hydraulic jack using a T shaped release valve, such as the one used on the Harbor Freight 20 Ton Air/Hydraulic Bottle Jack (item #59426).

Print at 100% infill and with 6 or more vertical shell perimeters. I use PETG for just about everything, but I'm sure most others would work.

This is a press fit on the valve of my jack, but using some JB Weld, RTV, or some other adhesive should keep it on there pretty close to permanently.

Ignore the dog fur on the jack. I have three German Shepherds, and dog fur on everything is pretty much unavoidable.

Prusa

No

0.2mm