How high can I stack my Banker's Box plastic storage contatiners?

Both the 0086201 and the 0086301 feature durable plastic construction with reinforced corners for added strength and can be stacked up to 5 high!

http://www.bankersbox.com/us/en/Products/Pages/product-listing.aspx?cat=RECORDS-STORAGE&subcat=RS_PLASCTIC_STORAGE&tercat=