these shocks are 300mm and will work perfectly on any maxi, newport, pinto, swinger, motobecane, peugeot, sachs, etc.
they will also work on a slew of other bikes - basically anything with a shock length near 300mm. please check for compatibility before purchase if you have any doubts.
they are super heavy duty with 3 adjustable settings.
treasured customer jay writes in from jamaica plains with this update --
thought i'd give you the lowdown on them from a moby standpoint -- these shocks take 10mm bolts, rather than the standard 8mm bolts that the stock moby shocks use, so anyone who buys these will need to pick up new bolts in order to make these shocks work. what this means is that it is also necessary to drill out original bolt holes in the frame so that the new bolts fit. in addition to that, these shocks are WAY wider than stock, so you have to make a couple spacers for the top and bottom bolts to keep the shocks straight and away the frame.
HOWEVER, these are so insanely fantastic and are about 100 times better to ride on than stock. The difference is really astounding. im riding a 50v with a hobbit front end and these in the rear, and all the sudden potholes, bumps, curbs, and manhole covers are no longer even a factor. SUCH a smooth ride, and a super-worthwhile upgrade.
the spring diameter is 48mm
VERY chrome VERY xtreme 
stiff 
Still bottom out