Material：Carbon steel、A2-70、A4-70 Surface treatment：Plain、HDG、Black、Dacromet、BZP、YZP Normal size：M4、M14、M16、M18 Matching C-channel sizes： M6: Fits 41×21 C-channel M8: Fits 41×21 & 41×41 C-channel M10/M12: Fits heavy-duty 41×41 and 52×34 channels