Stringvision Bowgrip for Violin-Viola-Cello stretches over all sizes without removing the frog. Yes- the height of bow frogs is very consistent, (even on incremental size bows) so one size truly does fit all bows.
Bastien Music Flash Cards by Kjos Music Company is based on the best-selling "Bastien Music Flashcards" (GP27) which have helped millions of students worldwide learn their key signatures.