The Fillikid bed rail (135 cm) is ideal for box spring beds, even without a slatted frame. It has sturdy, non-slip base holders that attach it securely to the bed, regardless of the presence of a slatted frame.
The grille has a length of 135 cm and is attached so that the two arms you can see in the picture are pushed under the mattress of the bed. So if the bed is longer than 135 cm and the bed frame does not overhang the mattress at the two ends where the arms are, it should fit.
The brackets of the bed rail are simply pushed under the mattress - so it should also work with a box spring bed. However, if the bed has a high frame or a high mattress, the grille is useless because it measures 43 cm from the bottom edge of the mattress to the top edge of the grille. The grille can also only be folded forwards if the bed has no frame.