This pack of 21 climbing holds are designed to be kid-friendly. They fit small hands perfectly and are poured in bright colors to keep them visually interesting. 21 holds will fill a 4x8 sheet of plywood or roughly 32 square feet. They work well indoors or outdoors (colors will fade over time in the sun). Fun Climbing: one trick to make climbing engaging for kids is to place a toy on an upper hold and have the kids climb up in order to rescue the toy. Share other games or tricks for fun climbing in the review section for other people to learn. When purchasing with hardware the package includes: 21 - 4 prong T-nuts and 21 - Stainless Steel Bolts.