Disc (easier to read) rather than ball type Anti-Freeze tester with plastic body and rubber bulb. Yes, the old glass ones are more retro but they break the first time you drop them- and you will.
Freeze protection level indicated by 6 x floating coloured discs. Easy-to-read temperature table. For determining levels of ethylene glycol anti-freeze so you can check condition of your coolant and if you need to top up or replace. Therefore it save you replacing all the coolant if it is ok and saves a potentially popped core plug (or worse) if it needed doing and you didn't check!