STMW Grille for 2015-2019 GMC Serria HD 2500/3500. STMW Grilles are fabricated using 10 gauge ASTM-A-36 main frame with 3/16” ASTM-A-36 center section, the strongest and thickest steel on the market for Grilles. The center of the STMW Grill is made with the highest quality hexagonal perforated, 16 gauge plain steel. All bolted together with stainless button head bolts. Shipping can take up to 4 weeks.