Can't find any on screwfix. They are made of white plastic, and fit in a groove routed into the sides of the drawers. They themselves have a groove along them for the drawer stop to move along, and have semicircular ends (making the whole thing like a very long oval). They are not the ball bearing type.
Mine are all split and shattered because they were fitted at right angles to the grain of the outer casing, and do not flex as much as wood. I plan to cut off (one of?) the locating pegs, and elongate the screw holes.
I can provide photos if nobody knows what I am talking about.
Does anyone know where to get them from?
Bob