Chews soft enough for a mouth that is still changing. Nothing in this collection is hard enough to threaten a tooth that has only just arrived.
Sensible from around four months, once the adult teeth are coming through. Before that a puppy is better off with something it can mash than something it has to work at.
What is deliberately not here matters as much as what is. No antlers, no hooves, no weight-bearing bone, not until the jaw has finished growing, which is somewhere between twelve and eighteen months depending on the breed.
Chewing is how a teething puppy settles itself, and giving it something appropriate is far easier than teaching it not to chew the skirting board.
Two rules. Supervise, every time. And size up rather than down: a chew small enough to swallow whole is the risk, not a chew that looks too big.
For matching the chew to the dog as it grows, read which chew, which benefit.