XL AUTO Collector's Edition - B Blades : There are two blades to a package.
Replacing a blade is easy. A Blades are for the Upper Head, and B Blades are for the Lower head. They have the same pitch, but the forward edge is opposite of each other, as one head rotates clockwise, and the other rotates counter clockwise. They all attach the same way.
First remove the screw holding the blade. Take note that the blade is loose in the Heads blade holder.. they flop about very loosely. Remove the bad blade, then slip in the new.
Tighten the screw down until the blade isn't loose, then back off until the blade flops easily. Easy, just don't lose the little screw. Tip : Work over an old white hand towel.. that way the little bouncing screws won't disappear so easily. If one does make it to the floor, try a pair of you wife's pantie hose ( ones she doesn't need any more.. please! ) Double it up and use an elastic band to tie it over the end of the suction hose. It often finds the invisible little things.