It’s foam sleeve to go over pipe to protect it from low temperature
Freezing kit will allow you freeze pipes temporarily. Freeze time will depend on pipe dimensions, pipe material and pressure in the pipe. Works well with cold water pipes. Not to be used with hot water pipes such as central heating. Average working time after freeze is approximately 20min to 30min.
It freezes pipe so you can work without draining system
A freezing kit can be supplied by screw fix it’s a freeze can and 2 sleeves for 15mm. And 22mm the clip around the pipe then cable tied either end the. The freeze can extension. Hose pushes into the sleeve. I normally use around half to 3 thirds of a can. Wait 10 minutes and then it should be frozen by that time