Both the SDKRDBS and SDKRDBL are flat dumbbell shelves that can any of the SDR Rubber Dumbbells, SDX Hex Dumbbells, SDP Pro Dumbbells or the Vinyl or Neoprene coated Dumbbells. The SDKRDBS has a surface space of 59" x 12". The SDKRDBL has a surface area of 59" x 18". The SDKRDBS is perfect for any size up to 100lb dumbbells. The SDKRDBL is perfect for dumbbells 105-120lbs.