Fixed dumbbells come with a fixed handle and weight, so no changes to the weight configurations are possible. The benefit of having a complete range of fixed dumbbells is that no adjustment is required between sets – you can simply move to the next weight range. Fixed dumbbells are also stronger and sturdier than their adjustable counterparts which make them more stable when using heavier weight, which is why they are the only dumbbells used in commercial gyms.
The rubber hex dumbbell is a regular iron dumbbell but with the head coated with rubber and shaped in the form of a hexagon (with six sides). This means they will not roll on the floor due to their shape; thereby providing extra stability and preventing gym injury from accidental roll off. The rubber covering also protects the floor of the gym from scratches and drop impact dents.