Echelon is packed in a small, windowed box, where you'll also find the mandatory paperwork, and a small, glossy, black case containing 3x10g & 1x5g weights.
The mouse itself uses an interesting rubberised coating, which gives it a very soft, velvety feel. If it wouldn't be for the digital camouflage pattern painted across it, I'd say Echelon is a really downplayed gaming mouse, with smooth curves, no unnecesary edges or "breathing" lights. I believe there is a small LED hidden under the DPI switch (I keep seeing blinking red lights), but since there's no transparent surface or wide-enough space to allow its rays to shine through, it's almost as if it isn't there.
Without any weights installed, the mouse is not really on the light side, although it's relatively small. If you would add the additional 35 grams, it becomes a genuine heavyweight.
On its underside, the mouse has three large PTFE slippy pads, two in the front, one in the back. The sensor is right in the middle, and next to it is a small button. Pressing said button will spit out a tray, which is where you will add the weights.
ASUS added 4 weights in the box, 3x10g and another one weighing only 5grams. Whilst the rodent itself clocks in at 101 grams on its own, once all 4 weights are added, it becomes a fairly heavy rodent.
I tested it on multiple surfaces, from glidey mats like the CM Storm Speed RX, or Tt eSports Pyrrhus, to the rough ones like the SteelSeries QCK Heavy. Overall, its tracking fared almost the same on every surface, with the exception of the QCK, where it registered a bit more noise. Even at its heaviest, the rodent glides as if it's weightless.
Echelon is a symetrical mouse, with patterned rubber coating on its side, adding some texture and grip. On the left side there are two buttons (back & forward), and two unassigned ones at left click's edge.
Since the mouse isn't really ambidextrous, the right side follows the same shape but doesn't really sport any side buttons.
I think Logitech spoiled me with G502's cable. Sure, Echelon uses a 1.8 meter long, nylon braided cable, but it's a very rigid one, probably the most rigid one I saw on a mouse. It is weighed however, and it does end in a nice gold-plated USB connector.
The symmetrical rodent looks like a fairly comfortable mouse, for certain grip tipes. It fits the fingertip grip and claw-grip best, with its raised bottom , symmetrical shape and short length. Since the side buttons placed too far back, the shape is almost generic, and it most assuredly isn't large enough, the average palm-grip user won't get much use out of it.
However, I have to ask, what's with the weight? Most claw-grip mice do not aspire to clock in 136 grams, and most users will like their rodent to actually sink under 100g, so that's slightly confusing. Still, since the weights are optional, and I can't say I dislike ASUS for giving us the option.