ah yes... the kitchen sink waste fitting game...
Of course the one that came with the sink wouldn't do easily so I thought I'd been really organised - buying a right angled "universal one" from either Ely or Lime-kiln (can't remember now)... there I was, poised ready to fit it to the bowl, only to find it JUST too small to make a reliable seal against the bottom.
Lateral thinking was required then - it being rush hour in town... INSPIRATION came in the form of using BOTH the one supplied AND the angled one (with 19mm outlet) I'd bought for the job. Luckily, whilst never really being a boy scout, I'm OFTEN prepared for
As luck would have it, the one that came with the sink fitted nicely (and was glued) into the one I'd bought - I THEN wrapped it with my favourite tool box backup: "self amalgamating tape" - it's marvellous... it lasts forever and so long as you put it on properly has never yet let me down.... come to think of it, it's even making a watertight seal around the boiler vent which goes out of our roof at home - *note to self... get up on the roof and check all is well there soon*.