Admittedly I haven’t had these for more than a week so I can’t attest to durability, but it’s clear to see these are extremely well made, and Kupo is a brand I trust. The design of these bags is just so well thought out, they effortlessly sit and come off stands, and due to the way they spread out the weight, and with the COG nearer your fist, they’re also easier to carry than traditional bags. Speaking of, the handles are amazing, though you won’t be able to grab as many bags at one time because of them, that said you really shouldn’t be doing that anyway.
There are situations where traditional sand bags are better suited, when you just need that mass of weight on things that aren’t traditional grip equipment, but in every other case, these are brilliant. They’re also super easy to fill, and the Velcro only opens if you want it to, you could further double stitch for extra assurance, like I said I can’t vouch for long term use, but I highly doubt these are going to break open any time soon.