What is the cartridge size?

	When choosing a cordless screwdriver, you are likely to come across the term "chuck size". Chuck size is not the size of the entire chuck, it refers to the largest shank diameter that the chuck can accept.
What is the shank diameter?
	The shank diameter is the measurement at the center of the bit shank. It determines if you can use a particular bit with your instrument. This measurement varies depending on the shape of the shank.
	Screwdriver bits always have a hex shank, which is hexagonal in shape. Hex shank diameter is measured through the center of the shank on the flat sides.
	Cordless screwdriver chucks come in two inch sizes: 1/4" (6.35 mm) 3/8" (10 mm)
	Simply put, the larger the chuck, the larger the shank diameter it can accept. You will find that most cordless screwdrivers have a 6.35mm chuck. This means they can accept screwdrivers or drills with a maximum shank diameter of 6.35mm.
	The 6.35mm chuck is sufficient for most home screwdriving jobs. If you're planning on doing heavier jobs like drilling, consider choosing a cordless drill/driver with a larger chuck.