The FSL is the larger of the two.
The other is not the NDL, but the Dynalite. (DL)
The DL has a much thinner .49" brake pad than the FSL of .800 and much smaller area as well.
The NDL is somewhere in the middle.
The alternate to both of these is a DynaPro which is booted for those who find this important. It's radial mount and with conversion brackets can be fit to the 12.2 x .81 TCE kit only. No 13s. It's listed as a sub option for about another $250. Very nice part too- low profile, stiff (better than NDL and way better than DL) and has .625 pads in them.
