Best OPK?

Looking to buy my first opk! Been TTC for about 5-6 months now and after having my last 3 periods start on time (or a day early) I'm using Glow to better track and hopefully bring us baby #2! Was just curious what you ladies are using and what kind of results you are getting? I really don't want to spend too much but I don't want to spend money on something that is cheap but isn't a good product. Thanks for any advice and good luck to all!