This is a limestone aggregate that is crushed in an angular fashion and typically comes in a size of 0.5 inches up to 0.75 inches. It is a little more uniform in size when delivered than #57 limestone. Both are used interchangeably but typically the more common one is #57 if size can be less uniform. The typical applications of #67 limestone gravel include driveways, walkways, French drains and other drainage controls, and concrete mix and applied before concrete is poured.