Effective defensive measure dating back to Roman times, these modern stainless steel representations remind us of the Ninja. Blackened to blend in with the road they were commonly used to defend fortifications and slow pursuers in battle. They are still used occasionally today by the military to slow vehicles with pneumatic tires by puncturing them. Light, strong and easy to carry. 1-1/2" x 1-1/4". Includes 2 sets of 10.