Thise Barometer has a brass case with super durable, tarnish-free coating and QuickFix fitting system (see below). Case diameter 6″, depth 2.5″, internal face 3.75″, external face 4.5″. Brass – an alloy of copper and zinc – is easy to work with, can be polished to a gleaming shine, and it has a high degree of corrosion resistance, making it the traditional choice of metal for use in harsh marine environments. 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. The unique QuickFix 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! QuickFix can also act to seal clock mechanisms making them waterproof.