Waterproof shower seal (to protect a cast or bandages) (Summertown OX2)

I think this item is a waterproof shower seal. The length is 66 cm. I think the blue strap is to ensure a secure fit at the top of the plastic around the elastic (as found on a YouTube video). It is old as found in a cupboard whilst at my parents house, but apart from a little yellowing, it looks in good condition. Collect from Kidlington or Summertown.