They are for house plants and what not, they have permeable membrane and are used for slow release watering. As the water is used up they shrink into tiny little balls and will expand again to their orginal state once watered, so they are reusable. I saw them at a garden show demonstration seemed pretty cool for a windowsill plant that is out in the hot heat all day with no attention. I wouldnt recommend them for mj cultivation. If your having issues with knowing when to water there is a seven dollar digital soil mositure meter that they sell at walmart nothing spectacular but its never done me wrong, and its alot more accurate than sticking my finger in the soil lol.