This type is somehow similar to single layer type by means of metal dome contacts attached under Maylar. But the difference is that, in this type, the Spacer is attached under the metal dome contacts. Air paths which function like air holes in single-layer, helps provide good click-feeling when dome contacts are pressed. Besides this effect, air paths help reduce the chance for PET film being damaged by metal dome contacts' burr and block dust coming into PET films.
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