Frame: mostly thermal-break aluminium — high strength, corrosion resistance and good insulation; the thermal-break strip separates inner and outer aluminium to block heat conduction and lower the heat-transfer coefficient. Glass: usually insulating or laminated; the insulating air layer or inert gas gives good insulation and soundproofing, and laminated glass is safer and also insulates. Hardware: handles, hinges, lock points and strikes; quality hardware operates smoothly and lasts, e.g. ergonomic handles and multi-point locking that strengthen sealing and security. Sealing gasket: seals between glass and frame and between frame and sash; quality gaskets have good elasticity, weather resistance and sealing to block rain, dust and air and raise air/water tightness.