Carriage bolts (round head with square neck) are commonly used in wood connections. We can provide carriage bolts/ Mushroom Head Square Neck Bolts as per following parameters:Grade: 4.6, 4.8, 5.6, 8.8, 10.9Finish: Auto Black, HDG, Zinc Plated, PTFE, Teflon, Xylon, Cadmium, dichromate, Rilson etc.