GE used a common body for the various U-boats, so this list is based on phases of the U30B.

Phase IIa- entire hood below the radiator is wider than the area ahead of it, radiator intakes are redesigned, the raised section on the radiator disappears, a horizontal drip rail appears on the sides of the radiator, short exhaust stack, large taper just ahead of the radiator, pipe chain guards at right front corner.

Phase IIb- the taper just ahead of the radiator disappears, six equipment doors on the left side instead of eight.

Phase IIc- the intake screens become corrugated instead of flat, and project slightly from the hood instead of being flush-mounted.

Phase IId- horizontal drip rail on the radiator disappears.

Phase IIe- built-up area on pilots disappears.

Phase IIf1- handrail notch in the stepwells becomes full length.

Phase IIg1- headlight casing becomes oval-shaped, not rectangular; cab side drip rail disappears.

Phase IIh1- square door laches become standard, battery box covers become smaller, cab door stiffener appears.