Here is another pair of dumbbells that replace multiple weights to save you space. The PowerBlock EXP Stage 1 Dumbbells allow adjustment from 5lb to 5lbs per dumbbell. These weights replace 16 pairs of dumbbells. They have an open design handle for increased range of motion.
These dumbbells have an auto lock function. They are made of welded solid steel. You can find out more about it here.