I have purchased one (20) package of these bottles, using them for both light and med-heavy oil mixes which are primarily perfume, cologne, and anti-age/wrinkle formulas. I can't speak to consistency between batches or lots, but performance and consistency within my first batch has been excellent. 15 (or so) out there with some of them carried in purses and/or luggage, and no reports of leakage thus far. Having received several unsolicited remarks on how the roller disperses evenly even with the medium weight oils, I can see no reason whatsoever not to recommend it as a very nice product, and a bargain at that.