It's a science extra credit question and I can't find the answer anywhere ! [:
what part of gravel are you having trouble understanding. OR Did I miss something in your question?
Foil: 0.1 mm Paper: 0.1 mm Wax Paper: 0.1 mm Rubber Gloves: 0.008 inch Plastic Wrap: 0.0005 inch Foam Sheets: not enough information they come in a wide range of thicknesses Cotton Cloth: fabric comes in different weights, which can have various thicknesses All the above thicknesses are approximate
