Given the shape of hex head bolts, they allow for greater torque compared to bolts that are circular. If you need these properties for a fastening project you're about to complete, make sure you find hex head bolts offering the following things.

Dependable Weather Resistance

Regardless of where you end up using hex head bolts, you want to ensure they won't damage prematurely because of weathering. In that case, focus on a weatherproof variety so that after these bolts are secured into place, they will remain there without breaking down due to weather elements.

You can find hex head bolts with a lot of different protective coats on them. What you can do is talk to a supplier that offers these fasteners, and then verify their coatings have weatherproof capabilities that are going to last wherever these fasteners are used.

Heavy-Duty Application Support 

Even if you don't suspect hex head bolts will be exposed to rigorous applications involving a lot of weight or force, it's still a good idea to get a variety that is meant for heavy-duty applications. Then you'll have even more confidence about the bolts being able to resist damage and wear over time.

The original purpose of these bolts was for heavy-duty use involving a lot of force, and that can give you more ways to use said fasteners in projects that come up. To verify heavy-duty application, you just need to see that the bolts are made from durable materials and feature great tensile strength.

Temperature  Resistant

If you plan on using hex head bolts around extreme temperatures because of the way systems perform around said fasteners, then you need to look for a variety with exceptional temperature resistance. That's going to keep the hex head bolts in sound shape structurally where they're not able to shift or have their dimensions thrown off in any major way.

If you know for certain the systems you're supporting with these fasteners will create hot temperatures, you need to verify temperature resistance before making a selection and putting in an order with a fastener supplier. 

There are a lot of great bolt types that can be used to fasten various materials for projects. If you want to use hex head bolts because of their shape, there are a couple of features you want to get that can ensure these fasteners work out for a long time and thus do not require frequent inspections.