I bought a pair of highly-recommended Kohler 1.6 gpf toilets. Both are
the first 1.6gpf toilets I've owned.

I also have 3 Kohler 1.6 GPF Wellworth toilets. Put them in our last
house too.
Ours are the oval shaped "comfort height" model.

We haven't had a problem, following the old

"If its brown, hold it (the lever) down"

The normal flush only uses half the water in the tank