SVL? Glass Screw Thread Tube, SVL? 42 thread

SVL? Glass Screw Thread Tube, SVL? 42 thread
Manufactured from 3.3 expansion borosilicate glass complying with ISO 3585 (ASTM E-438 Type 1 Class A)
The unique SVL? thread is a finer thread compared to GL thread
For use by glassblowers to construct apparatus with SVL? threaded joints
N.B.: SVL? threads are not compatible with GL threads