The P makes the difference
Penetration injuries are unpleasant and treacherous: you don't see a nail in a plank on the floor, and a regular sole won't stop it. The penetration-resistant midsole of an SBP shoe does, using a steel plate or a textile insert. Under the new classification, that textile variant is called SBPS or SBPL, depending on the nail thickness it was tested with.
SBP or S1P?
The difference lies in what else is required. S1P has, in addition to penetration protection, an anti-static construction, a closed heel area and an energy-absorbing heel. In most industrial environments that's the better choice; SBP is there for situations where those properties aren't needed.
