There is 2 types of clamps:
The worm drive style ones are reusable and can be tightened or loosened with a screwdriver. They don't close in a perfect circle though and could occasionally be the cause of small gas leaks.
The squeeze or stepless style clamps are single use only, they are tightened by squeezing the nipple on the side with pliers, wire cutters etc and close in a perfect circle. To remove you need to cut the clamp off, again with wire cutters or similar.
The 10.5mm stepless clamps fit our hose when used on barbed disconnects, barb and nut adapters, tap shank barbs and T-shaped line splitters.
The 12.8mm stepless are better for the M8 to Barb mini regulator outlet which has a larger barb.
The clamp tool is the best way to close the stepless clamps