Zenni is a good choice _if you know your PD_ (pupillary distance) - the distance from nose to center of pupil. 1 mm off will turn your glasses into headache machines. And the phone apps that purport to measure this are universally bad. Get it professionally done at a place that will give you the value. Costco will do so.

If you don't want to purchase online Costco is decent price - $180ish for the progressives lenses I just purchased vs $400+ from LensCrafters. Downside of Costco is a limited selection of frames, but worth a look. Also heard good things about Warby Parker but have not purchased lenses from them.

Oh, Zenni's progressive lenses have a much narrower distance vision section in the lens than Costco's. So I get progressive glasses at Costco then single reading and computer glasses (for < $40 each) at Zenni.