The transformer of free-weight dumbbells
The Stroops Bellitron is a multifunctional dumbbell set. They're dumbbells but they can also be converted in barbells and kettlebells. And because they don't roll like normal dumbbells, they can also be used as pushup bars.
To turn the Bellitron into a barbell you need two of them to connect the bars together to form a long bar. The bar formed is not very long though compared to traditional barbells. Each bar and plate is made of powder-coated steel and will not chip like cast iron.
Each dumbbell comes with 45 lbs of weight and can hold up to 85 lbs. The thing about the Bellitron is that taking off the plates and connecting the bars to form a barbell may be quite a hassle that it might be better off to just get a barbell. But if you want to be minimalist, this might be for you.