Hollow fibre restraining system

A filtration system, said filtration system comprising a bundle of hollow fibres and a restraining system for the hollow fibres, said restraining system comprising a plurality of longitudinally extending elements spaced from one another and supported by a plurality of discrete spacer elements, said spacer elements extending generally transverse of said longitudinally extending elements, wherein said spacer elements and said longitudinally extending elements are arranged to define a cage-like structure, wherein the longitudinally extending elements comprise rods and the spacer elements comprise rings, wherein each rod comprises a first width at a first location and a second width at a second location, wherein the second width is less than the first width, and wherein the rod engages with an associated spacer at the second location.