All of my Storage units are made to fit the New Larger Stampin Up ink pads. The Storage units are made of Solid pine with 1/8" hardboard for the shelves and backboards, very sturdy units. Each opening is 3-7/8" wide x 3-1/2" deep and 1" high.The shelves are also removeable to fit other items into the openings. The dowels come standard for a 3-1/2" diameter ribbon roll, if you need to accomodate the larger 4" diameter ribbon rolls, please let me know and I can customize that.