The most rational entry into home weights — rubber-encased hex dumbbells that don't roll, don't damage floors, and come in pairs from 2kg to 30kg. No adjustable mechanism to fail, no complexity, just weights that work. Buy pairs at the weights you'll actually use rather than a complete set you'll mostly ignore.
Bowflex's SelectTech replaces 15 pairs of dumbbells in the space of one — a dial adjusts the weight from 2.5kg to 24kg in 2.5kg increments, and the change takes two seconds. The most space-efficient home weight solution available, with quality that survives commercial gym-level use at a price that pays back in space saved within months.
Technogym makes the gym equipment used in five-star hotel gyms and Olympic training facilities — their adjustable dumbbell system uses the same materials and tolerances as their commercial products. The weight selection mechanism is the smoothest available, the balance is perfect at every setting, and the aesthetic is the most considered of any home weight system. Equipment that respects the space it occupies.