The build quality is awesome. It certainly stands up to a considerable beating from being chucked about. I started with pea gravel as the filler for one bag and used swimming pool noodles/woggles to fill up the left over space in the bag. By this approach I felt able to buy one ‘big bag’ and grow into it by adding other bags over time. I purchased the Brut Force Series: Basic training pdf. It is an excellent introduction to the “unstable load, odd object”(ULOO) training approach. If you want access to heavy weights, without the associated costs of standard metal weights you can’t go wrong with this piece of home gym equipment. 100% delighted.