I've been using the product for a week and can already measure that my eyelashes have grown half a mm with the ruler it comes with. You use very little product, most likely will last more than 4 weeks. Very easy to apply with the bent applicator. 

really great product

you have to be patient with it and apply as much as you can (everyday if you can before sleep) i saw some results over time = mny eyelashes grew much longer over like a month