I used sentinel for the last couple years(my sister uses it all the time), but, it got too expensive for me with 6 dogs(2 of them being outside and big). The vet was running a good sale last month on other kind of products, so bought a years supply of those instead. I can see which ones I like better, as last year the outside dogs never did have fleas on them, and we dont' have a problem with ticks |