Hi Jeff, All chains are actually the same sizes as the earlier British standard but are now measured in the metric system. I think the measurement you stated must be the outside width of the chain not the inside measurement which would be a tad over 3/8" Insidentaly the same thing applies to the Metric pipe sizes as in water pipe where the sizes are actually British standard pipe but now shown as metric. Just thought I'd add that as a bit of useless information..HAVE A GREAT AND SAFE AND PROSPEROUS NEW YEAR. Gerry