Both indoor engraved and outdoor engraved custom plastic signs are made of 60 mil thick acrylic. Where indoor engraved signs have the print engraved onto durable plastic, outdoor engraved signs feature print engraved onto textured, weather-resistant plastic and have co-extruded impact layers. Where indoor engraved custom plastic signs last for at least 2 years outside and are more pocket-friendly, outdoor engraved custom plastic signs last for over 20 years outdoors and cost a bit more.