Kangaroo Strop 3"x8". Magnetic-backed balsa-mounted strop. Kangaroo is an ULTRAFINE surface. Smoother than a baby's butt. It takes compounds extremely well and is EXTREMELY thin, minimizing inadvertent edge convexing. It's also an extremely strong leather. In particular, 'roo works exceptionally well with grits 0.125 micron and below because it doesn't provide much, if any, abrasion on its own, letting the compounds 'shine through.' It should work well enough on some of the coarser compounds, but balsa is more than adequate for those too. It also has a nice consistent draw.
The 3"x8" strop is mounted on magnetic-backed balsa. Extra-thin kangaroo leather was selected specifically because it is so thin that the amount of 'give' is minimized. Smooth? You bet! This is considered an ultimate strop, especially well suited for ultrafine compounds below one micron going all the way down to the finest compounds (0.025 microns - ten times finer than quarter micron). In the extreme, it can also be used without compound and has the 'draw' associated with leather. Pictures can't truly capture the smoothness, which must be touched to truly believe just how fine it is.