Thie is a uniquely styled 510 battery. I really like the battery due to its unique style, it's flexibility in settings, and its excellent battery life. Very pleased with this product. The only reason I gave it 4 stars instead of 5 stars is that it lacks any documentation. Basic instructions are included on the side of the package but a small insert with additional information like charge time, indicators, and the auto timeout function would have made this product perfect. It took me a few times using the product before I figured out all functions and how they worked. Very nice product though.