[Phlogiston]

Values of 8, 10 and up to 15uf will fit in many of the pre-1940 cans. The 15uf @630V is too large for most of the early cans that were 8uf and smaller.

The big 3 advantages are NP - don't worry which end goes where, 630V rating and the fact that you will never need to service the filter again. - - and a lot of little things like ripple current ratings.

I've been using them for around 10 years now.