The GDO nail grinder is a safe and easy to use alternative to cutting your dogs nails with clippers. Keeping a dogs nails trimmed keeps the “quick” or nail blood vessel, smaller allowing for shorter nail trimming. To use work the nail back and forth taking off just the sharp point. The GDO pet nail grinder is a great nail grinder for small to medium sized dogs. It's works on large dogs also, the progress is just a little slower with thicker nails. It is designed to maintain a length rather than take a lot of length off. With a rotating speed of 4500-7500 RPMs, it is one of the only grinders on the market with an adjustable speed. The battery is a rechargeable lithium battery that has the longest run time on the market at 20 hours. USB charging cable included. Battery takes 3.5 hours to charge.