To be used in all round hollow legs. For use on carpet floors. The foot is 35mm. The angle of the leg should never be greater than 30 degrees. Note: For use in square legs, read the measuring instructions carefully before ordering!Choose the correct size:Round TubeMeasure the internal diameter of the tube with a caliper.Square TubeMeasure the internal dimension of the tube with a caliper. Use the internal length and width, but also measure the opposite corner.Note: the dimension between the opposite corners should never be larger than the maximum dimension of the base part! If in doubt, please contact us.Not to be used with teardrop-shaped, oval & rectangular legs. (Here, the Footfixx Wood can often be used, which can be screwed into the current plastic cap.)