Sonor AQX 20 mm bass drum leg extension
I use them on my 18" bass drum with a 3d printed riser.
They slide onto the existing leg.
Simply printed upside down with no supports and 0.2 mm layer height
Tap the inside thread : I used an M10 tap (which doesn't fit the thread : it's probably imperial), and it locks itself into place because of the different thread pitch.
I polished mine to have a better look.
The author marked this model as their own original creation.