all the vase/lamp fittings have had the same length of spring fitting inside that I have and have seen , the only different one is the one on the link which was mines aswell but was a totally different fitting belonging to the vase lamp I bought with matching parchment shade and is the only one ive seen all the rest are the same as the one in the pic you posted belonging to shape RA which was a lamp vase that Keith purchased for me and which I have in my collection, if you look at the pics of the vase lamps on franks site you can see the fittings are all the same depth thru the glass, these were also domed on the top but some were flat but all had same depth of fitting collar