Security (of fit)
The HI-REZ upper consists of a single layer of breathable mesh underneath a thin hexagonal overlay that is more dense in certain areas to provide shape and lightweight support.  A burrito-wrap tongue and traditional lacing system are effective at customizing and setting tension in the midfoot area.  One drawback is that the combination of a burrito tongue and very thin upper can result in some gapping on the interior of the ankle – consequently, security through the heel is lacking on the curves of a track or on irregular terrain.  Security of fit is generally good through the midfoot and forefoot, although on several runs we had to stop and re-tighten the laces after about 30 to 45 minutes.  

Stability (on impact)
New Balance is careful to market the HI-REZ only as a road running shoe – which is important, because traction on anything but asphalt or an all-weather track is pretty bad.  There’s practically no outsole to this shoe; only 12 of the shoe’s 42 high-abrasion EVA pods have traditional outsole rubber on them.  The EVA is slightly dimpled, but there’s really no grip to them, and you’ll notice the slippage as soon as you hit dirt or gravel.  Used as directed, impact stability is fine, but there’s very little capacity for off-label use.  

Smoothness (flexibility)
Each of the 42 midsole pods are bonded to a durable, flexible fabric base that lets the contact surface flex at every gap between pods, allowing mobility and flexibility that mirror a completely bare foot.  Without question, flexibility is the strength of the HI-REZ.

Comfort
Like all shoes in the Minimus collection, the HI-REZ encourages sockless use with seamless construction and soft interior surfaces.  The toe box is quite narrow, preventing the toes from fully splaying, and even pushing the toes together at times – this led to minor friction blistering upon our initial use.  

One other comfort issue that may come into play is that aside from the EVA pods, the underside of the shoe is a single fabric layer that is permeable to water – so your feet will get wet even when running through shallow puddles.

Speed and agility
You’re hard pressed to find a lighter shoe on the market, so the HI-REZ is ideal for quick leg turnover.  However, if you’re on anything but asphalt, you need an extra measure of caution for traction and security.