Like the tone collar for trumpet, the DW cornet tone collar has superior build quality.
I tested it on two cornets of my own:
1) a Yamaha Xeno YCR-8335s,
2) a Besson pre-lottery Sovereign 927
Both are very commonly used in the UK.
The groove of the DW tone collar for cornet doesn't fit the Yamaha Xeno cornet, the cutting seemed to design for Yamaha cornet (the location is correct) but the size of the grove was incompatible. It fits better on the 3rd valve, fits poorly on the 1st valve.
It could fit on a Sovereign 927 but the groove doesn't fit anything on the cornet. It is held by the bottom cap. Denis Wick should provide cornet model compatibility chart before selling this cornet tone collar. If it doesn't fit a Yamaha Xeno nor the Sovereign 927, what was it designed for? Better fit and try in a store before buying one.
Because the fit is poor if you hold the cornet with a wide grip, i.e. you hold the lower valve casing, you might loosen up the tone collar by accident.