I kept Shetland sheep some years back and I found them to be very productive to keep. They were easy lambers, even to the terminal breeds of tup, and very milky. I put them to Blackie, Suffolk, Bleu du Maine, Border Leicester, and Texel tups and always got top money for my lambs.
The ewes were black and moorit................slightly bigger than the commercial type.
My friend (now deceased) kept a large amount which he bought from Shetland sheep sales at Inverurie, and his always did well to the Lleyn tup.