GSM (grams per square metre) describes the weight of the fabric — higher numbers mean a denser, heavier fabric. At 375 GSM, the Lush range provides significant light filtering. It's not a blackout fabric, but in daylight it reduces glare considerably and provides good privacy during the day. In the evening with internal lights on, silhouettes will be visible from outside, particularly in brighter colorways. If a complete blackout is required, pairing the Lush curtain with a blackout blind behind it is the most effective solution. For most residential rooms, the light filtering level is entirely practical for everyday living.