A brilliant gubbins to save space or odd ball fittings.
I used these excellent reducers to fit in the upward leg of a 22mm 'Tee' compression fitting, to provide a 15mm feed for a replacement radiator. Just one thing to be aware of they do not fit into very old brass 'Tee' fittings so I had to replace those as well.
Great if you need to step the size of pipe down