About the hardware purchase?
 

As we know, in fact the aluminum material some merchant asserted that is just the alloy material which contains some aluminum, also blend with some silicon, magnesium, the surface film thickness and surface treatment also will affect the price and the quality of the material. Oxidation, dull polish, electroplate, wood grain , baking varnish are the main surface treatments, and their prices are also differs greatly.

The main factor that leads to different prices is using different materials, the silver mirror colored with a bed of mercury then to mopping, and the general mirror is plated with a bed of aluminium then to mopping, the waterproof and fog efficacy decline a lot. Moreover, baking finish, stamp, tempering are also affect the mirror’s price.
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Aluminum in nature is never pure, because it's already a compound of aluminum with oxygen. Therefore, if a prime number KAC, it may reduce the quality of the product.