The Bell Spotter 500 Flip-up Flip-Down Training Wheels are designed for outdoor use and are suitable for 12" to 20" wheels on bikes. Made of plastic and metal, these white training wheels feature a flip-up design for when a child is practicing riding a bike without assistance. They are retractable and flip down when needed, making them ideal for beginner cyclists. This set includes mounting hardware and weighs 3 lbs, making it a convenient accessory for children learning to ride a bike.