This mechanical pencil lead is 0.7mm in diameter and has a hardness of 2B. It can be used with any of the 0.7mm pencil mechanisms sold by Bear Tooth Woods. HB hardness is about the same as a number 2 pencil. 4B hardness is softer and darker than the HB lead. 2B is between HB and 4B. It will create a darker line than HB but is not as prone to breaking as 4B. Each tube contains 12 pieces of lead.