Disclosed is a cylinder-retaining apparatus for a breathing apparatus comprising first and second fixing point and a strap apparatus secured to the first fixing point and the second fixing point. The strap apparatus forms a main strap loop for extending around and securing one or more cylinders. The cylinder-retaining apparatus is configurable in: i) an expanded configuration in which the main strap loop provides a first effective length for securing a first number of cylinders; and ii) a contracted configuration in which a portion of a strap of the strap apparatus is folded to form a secondary strap loop and the secondary strap loop is secured to a third fixing point such that the main strap loop forms a second effective length which is shorter than the first effective length and for securing a second number of cylinders less than the first number of cylinders.