Binoculars are used outdoors in nature, hiking, hunting, or birdwatching, you have to carry them. Therefore, they should be lightweight but made of a durable material that protects the instrument from the elements and guarantees perfect functioning. Housings and tubes of binoculars are made out of aluminum alloys, magnesium alloys or polycarbonate plastics which are usually coated with a non-slip rubber coating that offers grip and protection against bumps.

Aluminum alloy: The properties of aluminum; light, robust, durable, inherently corrosion-resistant, inexpensive, and easy to work with, making it a very suitable material for binoculars.

A high-quality material that is a third lighter than aluminum and has excellent properties. It is robust, durable, and corrosion-resistant. It is not as common as Al and requires somewhat more complex processing. Due to the slightly higher price, it is more likely to be found in premium models from high-end optics manufacturers, although there are exceptions.

Magnesium alloys are mixtures of magnesium with other metals which are then referred to as alloys. Depending on the application, different high proportions of aluminum, zinc, manganese, silicon, copper and zirconium are used. Magnesium is the lightest structural metal. A common alloy is Magnalium, an aluminum alloy with 5% magnesium and 95% aluminum.

is a polymer plastic that can be found in all kinds of everyday objects in any shape, application, and material properties. It is an inexpensive and easy to manufacture material that is easy to work with, corrosion-proof, stable, and very strong. High-strength polycarbonate bodies are typically used in many budget to mid-range binoculars.

Waterproofing And O-Ring Sealing

Unfortunately, as the instrument's waterproof rating increases, so will the price. To properly seal the entire assembly of a pair of binoculars, several seals and O-rings are required that are durable enough to withstand daily use in sometimes harsh environments for many years.

Water-resistant or weather-resistant

Waterproof and O-ring sealed: This is what you want! Waterproof and O-ring sealed means that all parts and assemblies of the binoculars are sealed, and that water and moisture cannot get in. Some binoculars withstand pressure and are submersible to certain depths. This is especially desirable for Marine binoculars.

fog-proof. This refers to O-ring sealed instruments where in the last manufacturing step, dry air (zero humidity), or nowadays often an inert gas such as nitrogen or argon is filled in, to prevent fogging.

Since binoculars are used outdoors in nature, it can only be an advantage if they are 100 percent waterproof and fog proof. Only then are they guaranteed to function reliably even under the toughest conditions.