Are twin slot brackets strong enough to support a shelf layout?

Twin Slot Shelving twin slot shelf brackets Twin Slot Shelf Bracket twinspin slot Twin slot wood shelf brackets to fit into twin slot 32 mm pitch uprights Chrome finish twin slot shelf brackets are sold in boxes of 25 pairs

twin slot shelving upright Twin Slot Shelving System Brackets Uprights with Metal Adjustable Racking and MDF Shelf for Home Organizer AA Channel $