When traveling to and from all day while carrying a laptop, you want a bag that does the job of transporting a laptop comfortably and securely. If you're looking for a non-bulky solution, a laptop sleeve, like the STM Myth, it's right up your alley because it completely protects the laptop with uninterrupted foam padding protection, as well as feature a handle and a shoulder strap to carry it like a messenger bag or briefcase.
The STM Myth laptop sleeve comes with a detachable webbing strap with two carabiner-style clips to attach it to the sleeve so, you can carry it on one shoulder or across the chest, messenger-style. The webbing strap seems to be made of the same material as the sleeve, which is 100% polyester.
The STM shoulder strap carabiner clips are made of rubberized hard plastic so, they have a touch of rubber finish on them. The shoulder strap carabiner quick-release mechanism seems to be made of metal alloy. The entire carabiner contraption sits on a rotable joint that allows the carabiner to freely spin around 360 degrees.
The shoulder strap carabiners attach to a webbing loop that is sewn vertically with reinforced stitching on to the top corners of the sleeve. The shoulder strap measures 1.25 meters long.
The zip pull tabs have STM branding on them and are made of soft rubber with perforations. The pull tabs attach to the zips with metal rivets, which is a neat way to add a touch of hardware to a bag.
There are two more metal rivets on either side of the brief and two more rivets, holding the grab handle, which is made of thermoplastic polyurethane (TPU) rubber material. Both TPU rubber and silicone rubber look and feel very much alike but TPU rubber isn't as flexible and bendable as silicone rubber.
The grab handle, by the way, it's constructed on the bottom of the STM Myth laptop sleeve brief, meaning when carrying it as a brief you are literary holding the laptop sleeve upside down, which isn't too reassuring because the zip is, essentially, supporting the laptop when carrying the sleeve in briefcase mode.
Having the zip at the bottom means that should you forget to zip up the laptop compartment and side compartment properly the contents inside it may fall through. While you do have to bear in mind that the zip is properly closed when carrying it in briefcase mode, it is nice that a grab handle is, at least, included.
The front side zip pocket runs horizontally across the sleeve and it's almost as deep as the main laptop compartment. Inside the front side zip pocket, there is also two wide elastic webbing loops.
Speaking of the main laptop compartment, it zips open via two zips, one of which can zip open to the corner edge, while the second zip opens almost all the way down to the bottom edge, which increases the opening of the compartment.
The STM Myth laptop sleeve is, definitely, a more feature-rich laptop sleeve compared to other laptop sleeves like the STM Ridge, which doesn't feature a grab handle or shoulder strap. With that said, the STM Ridge is perfect if you just want a "sleeve" in the true sense of the word.
The exterior material and styling of the STM Myth laptop sleeve is virtually the same as the STM Myth backpack version so, you get water repellency via two coatings of PU on the exterior and one PU-coating on the inner lining material. The polyurethane (PU) coatings on the exterior of STM Myth make the sleeve repel water but not completely because of the zip seam, which doesn't appear to be coated with PU; hence the STM Myth cannot be waterproof.
PU coatings are heavier than DWR treatments; hence PU is more often applied to bags, while DWR is more often applied to clothing gear. PU is more environmentally friendly than Durable Water Repellent (DWR) treatments, which contain not so friendly perfluorocarbons (PFCs). Another neat thing about PU coatings is that they add a layer of durable protection, making the fabric more resistant against wear-and-tear.

The Myth 15-inch laptop sleeve weighs 350 grams so, it's 50 grams heavier than the STM Ridge 15-inch version but then again, the Ridge laptop sleeve is not water repellent. The fleece lining material adds a nice touch to the Myth laptop sleeve.
Not only fleece is soft, fleece fibers are naturally hydrophobic (repel water), they are very breathable and they are insulating so, the Myth sleeve will keep your laptop protected against the cold.
The foam padding used in the Myth laptop sleeve is polyethylene, which is not to be confused with polyurethane, which is a softer, open-cell type foam whereas polyethylene is a firm, closed-cell foam, which does a good job at dissipating shocks and vibrations; hence why delivery companies use  polyethylene foam to package fragile goods.
The fact that the STM Myth laptop sleeve uses polyethylene foam is very reassuring and, even more so because the polyethylene foam encloses the entire STM Myth sleeve, including the corners.