The "Fitzroy" barometer benefits from a super durable, tarnish-free coating and QuickFix fitting system. Overall case diameter 15cm, depth 4cm. The instrument features a good quality aneroid movement and displays barometric pressure in millibars and inches. QUICK FIX - The unique Quick-Fix system allows the instrument to be locked hard to a bulkhead or wall but removed, in seconds, by hand. The instrument is supplied with a base plate which is screwed to the wall or bulkhead (instructions and drill hole template included). The instrument then simply slots over the base plate and with a gentle twist, is locked on. A reverse twist removes it again. This makes changing batteries easy, removal for storage easy, and avoids the tricky job of not scratching your polished case when screwing the instrument to the wall! TARNISH-FREE - Tarnish-free instruments have been coated with a newly developed protective coating using advanced surface treatment technology. Far superior to lacquers and varnishes, it can withstand more than 720 hours (the longest test period for this process) under NSS (Neutral Sea Salt) laboratory testing. NSS testing is a certificated and standardised test method used to check corrosion resistance of coatings on metals such as brass, zinc and steel. This means your instruments will stay looking good for longer even when exposed to the harsh marine environment for extended periods.