Thanks Max and Taylog1
I agree with you Max about the height issue, it is a slightly longer (1cm?) chimney height in the blue vase. But I have often found height issues in factory glass, remember my 'Sandringham' candlestick in blue that was just over 5" in height, when most are 4.5" - it was the real thing with Wedgwood marks to base, Nigel Benson said it happens occasionally (see thread). Picture is purely as evidence that height differences can occur. Of course in the white and blue vase we are dealing with, it is more a proportion difference as the height is the same for both 18cm

this item is over 5" when most are 4.5"
Taylog1 - Thanks, I state these vases are described as cased in the Designlasin. My white one
is cased, and although you can't see it that well the blue one
is also cased (to the same level), I have handled it recently so as to measure the proportion (diameter) of the distensions. They are the same for both vases give or take a mm or two - the height at which distensions occur is slightly diiferent in the blue vase, as the chimney is a bit longer.
Thanks
Adam P