3/8 X 2-3/4" Sleeve Anchors | Combo Drive | Flat Head | Zinc Plated Box 50 Size:0.375" (3/8") The Black Phosphate coating is

The Black Phosphate coating is used to reduce friction during installation and increase corrosion protection

weld and flame cut grinding

Phosphate coating protects the fastener from corrosion although it is recommended that they are used for interior use only and not in treated lumber

On a “cost per pound” comparison

3/8 X 2-3/4" Sleeve Anchors | Combo Drive | Flat Head | Zinc Plated Box 50 Size:0.375" (3/8") The Black Phosphate coating isEmbedment: 1 1 2 Tension (lb): 559 Materials: Aged brick, block, drywall, masonry or Concrete. The ideal anchors for fastening applications that require medium pullout values. Our sleeve anchors are good for applications include attaching door and window frames, stair rails, steel ledgers, storage racking and electrical junction boxes. ANCLA DE MANGA TUERCA HEXAGONAL