... .3x48.3mm with EN74 standard,It can with groove or not,You can choose as you need.2.British ... 3x48.3mm with BS1139 standards,and you can choose the nut size.3.German type coupler with EN74 standards.The ... 48.3x42mm and 42x42mm.74x48.3mm,74x74mm,76x48.3mm,76x76mm Or other size you may need.4.All the coupler ... have our own model workshop,So if you have a drawing or other design we can open new model.8,We ...