10.5mm Stainless Steel Stepless Clamps (suit 7-10mm OD)

Sold individually or as a 20 pack Stainless Stepless Clamp (suit 7-10mm OD) 10.5mm

These clamps suit 8mm (5/16") or 9.5mm (3/8") OD line. 

They are sometimes called Oetiker clips.

Stepless clamps are designed to tighten in an exact circle around the hosing, simply use a crimping tool or the middle cutter on your pliers to crimp the stepless clamp closed.

This creates a much better seal compared to jubilee clips that aren't suitable for small diameter lines used in beer dispensing / homebrewing (as the jubilee clips have a flat section which will often leak).