Judge system-window quality from five aspects. (1) System completeness: a genuine system window has a defined system name, R&D documentation and unified component markings, with all parts matched and tested; if a seller emphasises only a single component (e.g. thermal-break aluminium) with no system scheme, it may be a 'pseudo system window'. (2) Core components: profiles should be 6063-T5 aluminium with wall thickness of at least 1.4 mm and PA66 nylon thermal-break strips (not PVC); hardware should be a well-known brand (e.g. HOPO, SIEGENIA) in 304 stainless steel; gaskets should be EPDM; and glass should be 3C-certified tempered insulating glass with double sealing and no bubbles. (3) Performance indicators: check the third-party test report, focusing on the 'five properties' - wind-pressure resistance of grade 5 or above (high-rise), water tightness of grade 3 or above (rainy areas), air tightness of grade 7 or above (severe-cold areas), a K value of 2.0 or less (northern insulation) and sound reduction of 35 dB or more (street-facing). (4) Workmanship details: corners should use pin-and-glue injection with flat edges; the surface coating should be even and scratch-free; and the frame bottom should have covered drain holes that flow freely. (5) After-sales warranty: profiles and glass 5-10 years and hardware over 5 years, with installation and after-sales support; avoid products with no clear warranty.