These sockets are rated at 210 degrees Celsius (see the 'T210' mark on the socket itself). I was not sure if these sockets were really up to European standards, so I decided to double check and simply put two sockets on thin foil in the middle of an oven at 200 degrees Celsius for 15min. The threaded piece and the ring maintained shape, but lost a bit of strength. Both caps on the other hand totally melted away! These sockets are not that safe I guess...
All Good