Our large (almost 4 feet!) 11½" x 43" Keyboard magnets are specially laminated to be used with dry erase markers.
 
These unique magnets were created with visual learners in mind.  When applied to any magnetic dry-erase board, the instructor indicates and displays note names, scales, chords, etc by using a dry-erase marker to fill in the appropriate areas.  Redesigned now so there's plenty of space to write enharmonics.