This is a replacement protective front bumper for your quad skates. Use a hair dryer to make the rubber warm and use super glue to attach it to the boot. 

The protective bumper comes as a set of two bumpers (left and right). 

Please check what size bumper you need:
S (size13/31 -  size3.5/35.5)
M (size4/36 - size7.5/40)
L (size8/41 -  size13.5/51)