Bowflex includes a two-year warranty on the weight plates and parts. Amazon shoppers are working up a sweat: The dumbbells have 19,000 five-star reviews, while the kettlebell has over 6,000.

As popularised by Bowflex, this kind of instantly adjustable dumbbell – no fiddling about with collars and weight plates here – is an excellent solution if time and space are at a premium for you.