The 50 Mg spool does fit and work in the 100B. It is expensive and it will increase performance due to it's lighter weight. This will enable the spool to reach higher sppeds with less energy resulting in a easier and possibly longer cast. It will also allow you to throw lighter baits with less effort.

All the new stuff is usually unvailed in July at the ICAST show in Las Vegas.I'm sure we'll hear about it soon