Pretty basic sofa leg. 50 mm diameter, 40 mm tall. Presses into a hole about 14 mm diameter. Chamfer at the bottom, mostly for looks.

The originals were lost in a move, so I mocked up something that worked and was similar to the other sofa in the room. 

Dowel is 13.4 mm (across the flats) octagon, which is 14.5 mm the long way. I made it octagonal because it it easier to modify if needed to get it to fit. If it's a little bit too big it's easier to sand the corners off an octagon than a cylinder. Chamfer at top with a very slight (2 degree) taper to ease installation. 

Printed with two line walls and 20% infill. Has been in use for about a year without breaking, so it seems to be strong enough.