Can someone address how this actually installs? Do you just push the spikes into the ground or do you have to use spikes?

The spikes are built into the edging, so it's a matter of connnecting the sections together and using a mallet to hammer down. Digging a small trench line makes installation easier. Video below:

Install Video

Does 6” width include the support teeth ?

The 6" is what is above ground. The spikes are a little over 4".

Is it possible to put a 90* bend in one of the pieces?

Yes, you can make a 90 degree bend.  You would need to secure the piece of edging (with a vice or some other means--I've just stood on the end of the piece and it worked fine) and bend the edging using a mallet against a blunt edged object such as a block of wood.

what gauge is the steel?

It is 14 gauge steel.  1/16" of an inch in thichness.

Can I create a 10ft radius with the 150mm product?

Yes, you can make a 10ft radius with the 150mm core edge.  I even found the equation that we spoke on the phone about.

If you know the circle's diameter, multiply that number by π (pi) 3.14 to get the circle's circumference.   So if the diameter of your circle is 10 feet, you'd calculate 10 × 3.14 = 31.4 feet as the circumference.