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Useful for pressurizing the fluid reservoir, makes bleeding or a complete brake fluid flush a breeze.

Main threads should fit most European brands (at least the internet thinks so) but I have tried it successfully with several Volvo's of different vintages.

I printed mine in PLA for strength, layer adhesion and ease of getting the quite steep overhangs good. Time will tell if brake fluid degrades it. Also I printed it almost solid.

You will need an air hose fitting with a BSP (G) ¼" thread and a rubber gasket. You can make one from gasket material or take one from an old reservoir cap.

When using, make sure to turn the regulator down sufficiently, I don't think the reservoirs are made to take a lot of pressure, 1 to 2 atm relative pressure should be plenty.