every once in a while, one of the pads may be malformed and won't work right. the frequency of this defect is approximately 1 out of every 15 pads. sometimes the polish solution is too watery (approximately 1 out of every 5 bottles), but it's still usable; more solution has to be used when it's watery, so it's not as cost-effective. for my business purposes, even with the occasional defective pad and watery solution, these supplies are an adequate value.