The LimbO Child Arm Waterproof Wound & Cast Protector will seal above the cast. The arm cast cover can with confidence be used in baths, showers, pools and most circumstances where you need to keep your wound or plaster dry. This LimbO protector will seal just above the top of the cast and can be fully submerged. Sizing Guide for arm cast cover Measure arm circumference 2cm above the cast -Please note, some child full arm casts can be very large and bulky around the elbow area