PU wheels, or polyurethane wheels, are a common type of wheel used on roller skates, inline skates, and longboards. They are made from a synthetic material called polyurethane, which is known for its durability, flexibility, and good grip on various surfaces.

Here are some key characteristics of PU wheels:

1. Durability: PU wheels are quite durable and can withstand the rigors of regular skating, including jumps, grinds, and slides.

2. Grip: They provide good traction, which helps with stability and control, especially when turning or skating at high speeds.

3. Softness/Hardness: PU wheels come in different hardness levels, measured on the A scale (e.g., 78A, 82A, 85A). Softer wheels (lower numbers) are better for smooth surfaces and provide more shock absorption, while harder wheels (higher numbers) are more suitable for rougher surfaces and offer better speed.

4. Performance: The performance of PU wheels can vary based on their composition, size, and shape. For example, larger wheels are typically used for cruising and long-distance skating because they roll faster and smoother, while smaller wheels are often used for agility and tricks.

5. Noise: Generally, PU wheels produce less noise compared to wheels made from other materials, making them a preferred choice for indoor use.

When selecting PU wheels for your roller skates, it's important to consider the type of skating you will be doing, the surface you'll be skating on, and your personal preferences regarding speed, grip, and comfort.