You are correct, at least partially. As it turns out, they actually are the same size, but the 70L sender gives different resistance values. So, for my car, the warning light will turn on at the right point but the needle only goes as far as the 1/4 mark if that is what it denotes. Unfortunately, I once again need to buy a sender. This one is good so I'm going to sell it in the parts section if I can.