Green Tea Extract - Good or bad?

Hi, I've been taking these Green Tea pills and I'm really not sure if they're good, bad, or I'm just wasting my money.

Here's a run-down of the ingredients: (Per caplet) Green Tea Extract (20:1) 42.5mg, providing 850mg, maltodextrin, magnesium stearate, capsule shell.

Any info/advice would be very much appreciated. c: