BOOMWHACKERS are a fun way to create rhythmic melodies in class. Simply tap on a surface and listen to the note resonate. Easy to play, durable and built to beat. These Boomwhacker Octavator Tube end caps will lower your tune pitch by an octave and is a perfect way to expand the tones of your Boomwhacker set. Sold in pack of 8 caps. OXYGEN Music specializes in all school percussion and band instruments, including a range of Boomwhacker Sets and accessories like these Octavator End Caps.