M 6 x 50 Coach Bolts/Carriage Bolts + Nuts. Bzp. (6mm diameter x 50mm long from under head including square part of shank). Pack 50. Low round head with Square underneath to lock into wood. Suitable for Timber to Timber or Timber to Metal connections. The bolt is inserted in pilot hole & as the nut is tightened it pulls the the square section of the shank into the hole/wood and & locks it leaving a low domed head finish.