These clamps are the golden standard in what comes in your Kegerator kit, and used widely for 5mm ID and 6mm ID x 8mm OD beer and gas line. If you are using 4mm ID x 8mm OD beer hose, you will need to purchase the 7-10mm (10.5mm) Clamps as the internal wall is thicker and won't fit over the clamp.
Stepless clamps are designed to tighten in an exact circle around the hosing, sinply use a crimping tool or the middle cutter on your pliers to crimp (not squeeze) the stepless clamp closed.