For example, if you have 25mm/1" webbing, you need 25mm/1" buttons. Buckle size = webbing width. Plastic 3 Bar Tri Glide Sliders Buckle Fasteners For Webbing. ID:16mm 20mm 25mm 30mm 32mm 38mm. The slider buckle is made of durable and lightweight plastic, so it can be used for long-lasting purposes.