What GSM and fabric composition should a 3-layer hardshell jacket use for 4-season use?

A proven 4-season 3L hardshell specification: face fabric 20D–70D nylon or polyester (heavier denier for abrasion zones), a waterproof-breathable membrane, and a tricot or mesh backer — total weight around 150–250 GSM.

Performance targets that hold up across seasons: hydrostatic head of 15,000–20,000 mm and breathability of 10,000–20,000 g/m²/24h (JIS L 1099 B-1), with a PFAS-free C0 DWR on the face. Below roughly 150 GSM total weight, 2.5-layer constructions usually deliver better value; above it, 3-layer earns its cost in durability. Ask the factory for test reports per fabric batch, not just spec-sheet numbers.