Title: Better than no cover but not by much...
Review: As other reviewers have stated, there are "drain holes" in the cover. They're pretty large in my opinion (about quarter sized, give or take) and do allow quite a lot of dirt/insects into the pool despite the cover being on. This could possibly be remedied if the holes were all mesh covered, however, on the one I bought (10' size) *none* of the holes have mesh. The 12' cover seems to have one larger drain hole in the center that is covered with mesh vs the dozen or so completely open holes that the 10' cover has scattered around the top. If I could find the box for it, I would probably return it and try the 12' cover, since the 10' is pretty large on the 10'x30" pool anyway.
Is this product review negative?