It can be used for ages 3 months until the baby takes steps around furniture or baby's measurement from top of head to tail - bone reaches 21 inches or baby weighs 30 lbs — whichever comes first.
I had been using these for a few years with my Doxies and Labs, I noticed one day that one of my small dogs was choking so I pulling out about 4 inches of the tail end chewed around a very sharp bone.