Curve Rod Sticks Nail Guide for Acrylic or Gel Application. After modeling nails with forms, these rods is the latest handy tool to fix that C-curve. They are made of aluminum with special anti-rust coating. Rods in different sizes. The diameters of each 120 mm long and anodized aluminum sticks are: 5, 6, 7, 8, 9, and 10 mm.