Heating Element Thread/Locknut Question

I've been following many DIY posts regarding installing heating elements and just want some clarification before I place an order...

The base of the element requires a 1.25" hole (step-bit) in a keggle (for example). I picked up a Camco element at HD the other day and did a quick measurement of the base and came up with 1.25", great. What I'm perplexed about is the Stainless Steel Locknuts (straight threaded with groove for o-ring) advertised for heating elements at BargainFittings states that the 1" fits electric water heater threads. Is this correct? Am I missing something????

I think mine came from bargainfittings too and it works like a charm. I'm not a master at all the different fittings types, etc, but the one they refer as the heating element one is perfect and I've been using it for a long time now.

1" nominal, not literally. http://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html

1" Lock Nut
1" coupler
1" half coupler

They all fit.

Thats what I figured. Thanks.