Block Division’s numbering system is an easy to use methodology for part numbers. The first part of the numbering system is the sheave diameter (in inches). The next part is the style (eye, flat, fixed eye or hook), followed by the number of sheaves (single, double, triple). The “SN” at the end indicates whether the product is a Snatch Block, while the letters “SL” at the end indicate if the product includes a Safety Latch. There is also a “C” for Card pack.