The opening is small but after a few tries it gets easier to curl my lashes. The charge lasts for many days, I think it’s been a week and it still heats up. My lashes are very straight and they uncurl after 30 minutes or so (using a normal curler). With this curler, the curl does not last a full day for me but at least it holds them up for about 6 hours. I’m happy with the result.