These buckles are non-adjusting, meaning that each buckle end has only one opening. They're perfect for paracord bracelets, and can also be used for applications where webbing doesn't have to be adjusted. They have 1/2" (13mm) openings for nylon, plastic or cotton straps.These buckles were designed specifically for paracord bracelets! They have slots that are wider than normal to allow paracord to be easily threaded through.  Slot is 3/16" (4.5mm) wide