T-Bolt and Collar Nut KOVA Manufacturer all types T-Bolts with Special nuts used in Couplers. T- Bolts and Collar Nuts are the components of German type couplers.– Grade 8.8 bolt and flange nuts, Nuts size 19mm/22mm– Hot dip galvanized• M12x70 SW21. https://www.kova.in/t-bolt/