Extruded and CNC-machined from 6061-T6 aluminum, Box Two™ Stem Spacer Kits feature an ultra-minimalist design that is super lightweight. Weights range from 0.02 to 0.14 ounces (0.56 to 4 grams), depending on the size. For the best performance, stack the spacers so the vertical supports are in alignment. Sold in packs of five, each set provides spacing adjustments from 1 to 20 millimeters.