EHOUSE Pest Control Ultrasonic Repeller Electronic Plug in Best Repellent Get Rid Of - Rodents, Mice, Rats, Roaches, Spiders, Bed Bugs & insects, Has a USB port, Use Indoor & Outdoor, in Car It stays sharp up to four times longer than standard chains This chain a low-vibration chain with a reduced kickback tendency. It is especially good for cutting dirty wood, treated wood, roots and hardwoods, which would quickly dull conventional chains. This chain must be re-sharpened with a formed diamond grinding wheel.or diamond grinding stones size 7/32"