STL1 is a specification for a 132 kV towers, belonging it appears to the former North of Scotland Hydro-Electric Board. No details are known, but two tower suites are known to be compliant with this specification based on the general arrangement and erection diagrams (GA&ED):
- A Blaw Knox tower suite that appears to be the same design as the CEB L132 submission that became SWE PL16
- Eve 0.175, itself also compliant with CEB L132
The relationship with and any major differences between STL1 and L132 are not known.