Yes,I have bought those vials of advantage for dogs which come with a syringe so that you can very very cheaply treat your cats for fleas.
I'm a cheapskate,been doing it for years but ya really must trust who yer buying from.
Any thoughts on those ebay flea meds?

I've done the same thing. I'm a breeder, so I have more cats than average to treat than the average pet owner. Sometimes these meds are good, but sometimes they come from overseas and the potency is different, so they don't seem to be as effective as those from the USA. Now I order the same LG dog size, but I get it from a US source that I trust. Revival Animal Health. I would rather get something that works than take a chance on not getting anything.

Just be careful with buying them from ebay, pet stores and other retailers. I have seen many animals come into the hospital that I work at with hair loss, high fevers, apetite loss and even seizuring because of this.
But on the other hand if you have found someone you trust and that it works, stick with it and let others know of trusted sellers!

Also, the expiration date is usually expired with ebay.

I would spend a little more and get something that I know is safe.