The U-shaped plastic- coated wire Hasp is what holds the EVA non-rigid plastic Bock's Boc-Loc dewlap tag in place.
The metal hasp is covered to prevent infection, and it cannot rust.
Allflex Accessories - White Marker Pen
Allflex Accessories - Black Marker Pen
Allflex Accessories - Tag Removal Knife
Allflex Applicator - Total Tagger Ear Tag Applicator - For 2 Piece Tags (Red)