This product is made of soft elastomer material， suitable for basketball football and other professional sports fitness.
size
M: length of about 39cm， small mouth circumference (telescopic range 16-26cm)， big mouth circumference (telescopic range 23-36cm)
L: length of about 41cm， small mouth circumference (telescopic range 18-28cm)， big mouth circumference (telescopic range 27-40cm)