After extensive consultation with the magazine industry and other mail users, and tests of various samples, Canada Post has released new recommendations for the weight and dimension of business reply cards (BRCs; bind-in, blow-in). Its original announcement in July 2011 caused some consternation when it required heavier weight stock but has now been amended to say that
After substantial testing and analysis, we would like to advise that Business Reply Mail customers may continue using paper with a weight lower than 160 gms but not less than 111 gms. In such cases, customers must realize that a small portion of their returned cards may be subject to longer processing times. To improve performance, we recommend using: optimal card size of 108 mm x 165 mm (4.3 in x 6.5 in); and grain direction long.
According to a memorandum from Magazines Canada, the problem Canada Post was (is) trying to avoid is that, in order to reduce mailing weights, some publishers were printing BRCs on so light a stock they were fragile and were either damaged or destroyed in the mail sorting process or they are jamming equipment.