The most basic arrangement for a back-mounted set consists of a metal or webbing strap around the cylinder just below the shoulder, and another lower down the cylinder, to which webbing shoulder and waist straps are attached. Shoulder straps can be of fixed length to suit a particular diver, but are more often adjustable. Sometimes a quick release buckle is added to one or both of the shoulder straps. The waist belt has a buckle for closing and release. and the waist belt is usually adjustable for security and comfort. Various attachments have been used to attach the harness straps to the cylinder bands. A crotch strap is optional, and usually runs from the lower cylinder band to the front of the waistband. This strap prevents the set from riding upwards on the diver when in use. This arrangement is still occasionally seen in use.