Bidirectional Road Stud For Road Safety-Nokin Motorway Road Studs or Bidirectional Unidirectional or Bidirectional 360º Lighting SR-i15 SR-i20 SR-i35 Ready for Snowplows Raising From Road Surface.5" (12.70mm) .59" (15.00mm) .67" (17.00mm) Mechanical Resistance 60 Tons 20 Tons 18 Tons i-STUD Technology LED Type Standard Standard Standard