For a little history on them, but not getting to specific because I'm lazy, They were originally developed here in the U.S in the 1960s. The Canadian military licensed the design, but produced the mags themselves using a lesser plastic. Most of the bad reviews on these mags are the Canadian made ones that are hit or miss. The ones produced here in the U.S. by Thermold/Master-Mold are made of Zytel and are very durable.
More information can be found here and here
More information can be found here and here
Last edited: