Actually Suture sizes are described most commonly using the USP (United States Pharmacopeia) denotation. Using this system, sutures diameter is described from 11-0 (smallest) to 7 (largest). The numerical USP system worked well when there was only a few larger suture materials (size 1, 2, 3, etc..), but as technology allowed for smaller and stronger suture mature, the number system became confusing. The suture material smaller than the USP size 1, is 1-0 which is pronounced as 'ought' and smaller yet is 2-0, meaning 00 (pronounced 'two ought' or 'two zero'). The more zeros, the smaller the material, so 6-0 is actually size 000000, and is pronounced 'six ought' or 'six zero'. It is important to note that the USP dimensions for catgut are different to those of other sutures. For example, 2-0 Catgut is larger than 2-0 PDS. Same problem is faced with catheters,gauzes and angiocaths.
