Black Twin slot Shelves Storage & shelving

Does anyone know if twin slot shelving is a standard ? I have some brackets from B&Q but they didn't have the tracks in stock Screwfix do but

Twin Slot Shelves or in the ever-popular white: White Twin Slot Shelves We offer brackets and uprights in two colours: white and black, to perfectly

blackjack classic perfect pairs slot Heavy duty twin slot shelving from Wall mounted modular shelving that's easy to install & customise Next day delivery, free delivery over £30

black 4 slot toaster Twin Slot Shelves or in the ever-popular white: White Twin Slot Shelves We offer brackets and uprights in two colours: white and black, to perfectly