just trying to fix my kitchen tap.
so i've disassembled the tap completely. took me a while to figure out there was a tiny screw holding the inside together. all seems good, but the teeth inside no longer open the tap.

basically, my temporary solution of using mini pliers on the spline has sanded the teeth down. it's just a smooth cylinder now. so i'll need to replace the whole cartridge. which means i need a spanner.

how universal are these things? can i just measure it, order the same size one, screw it in there?