These have been going round the school playground for the last two weeks and I finally gave in to getting my son one, who's 8. Concerned about the ones with metal cores, these are apparently meant for the more experienced users, we opted for this inexpensive version. It's sturdy enough, weighty enough and he hasn't stopped playing with it, as they do.
BUT more IMPRESSIVE is I ordered it at 5.15pm last night and it arrive at 8.40am this morning!!!
Haven't rated as durable yet as only just got it but seems sturdy, probably the thing to wear out is the nylon string but that can easily be replaced if need be.