Abstract: A ring binder mechanism having two carrier rails which are arranged in a resilient casing member and which bear against each other, the angle formed between said carrier rails changing from an obtuse to an acute angle and vice versa during opening and closing of pairs of half rings associated with said carrier rails, wherein the casing member has a connection point in at least one end of the casing for connecting the casing to a support and the casing member is strengthened by at least one channel or bead extending from within a recess about the connection point to a point between the recess and the pair of half rings closest to the recess.