This is the style I'm on about, look closely at the air dial and the 40 PSI has a wide range around it.
Similar ones but are high pressure and they claim and upgrade to 220 or 300 PSI (for bloody MTBs and balls FFS).
they make it harder to get a good reading of 38, 40, 42 psi etc when tweaking.
but double check descriptions and prices. https://www.ebay.co.uk/itm/254039956279
but for testing, just slap some pressure in, the forks take over 100PSI which is used when testing and fitting new parts.
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