On Friday, 22 March 2019 08:40:58 UTC, MM wrote:

Sure, but we're talking about what is available to the end consumer
here. All the tap valves I've seen (B&Q, Screwfix etc) are either
shrink-wrapped or in a sealed plastic bag, which makes counting the
splines very difficult, if not impossible.

Since there are up to 23 different combinations of spline count and
diameter, as per the above gauges, finding the right one for a
particular knob must be nigh on impossible.

MM

why is there no BS standard for this?