I've just found a discrepancy between the 2 of these I own (for use on a whiteboard, where they consistently reside with no warping or stretching). Laying the cm/mm edges together, one ruler's 30cm is the other ruler's 29.4cm. Likewise, 1234; on one looks like 11.7534; on the other. For a product that professes to serve a measurement function, 2 is a pretty big difference! Neither of these is accurate; a professional rigid ruler puts the truth between these two, although one is a bit less inaccurate. If it's the second one I bought, Westcott may be improving on quality control, but I have no way of knowing which is the earlier purchase. This kind of thin yellow magnet may still be helpful for marking out regularities (marking a dot every lets-call-it-two-inches, for example).
Rating: [3 of 5 Stars!]