- Weight
- Measured in grams for a men's US 9. Under 220 g feels racy; over 290 g reads as a tank. Weight matters most as pace rises — on easy runs, cushioning wins.
- Drop
- Heel stack minus forefoot stack. High drop (10–12 mm) shifts load toward the knee; low drop (0–5 mm) loads the calf and Achilles. Change it gradually.
- Stack height
- How much foam sits under the heel. 25 mm is ground-feel territory; 40 mm+ is max cushion. Taller stacks protect legs but can feel wobbly on turns.
- Flexibility
- Rated 1–5. Rigid shoes (1–2) roll you forward through a plate or rockered sole. Flexible shoes (4–5) let your foot do the work — better for short, natural strides.
- Toe-box width
- Forefoot room at splay. Narrow suits low-volume feet and racers; wide and very-wide suit bunions, swelling on long runs and natural-shape preferences.
- Cushioning
- Rated 1–5 for perceived softness, not just stack. Two shoes with the same stack can feel firm or pillowy depending on foam compound and geometry.
- Intended pace
- The effort band a shoe was tuned for. Plated racers feel dead at 11:00/mi; plush recovery trainers feel sluggish at 6:30/mi.
- Carbon plate
- A stiff plate stores and returns energy, but only at speed. Carbon belongs in race and tempo shoes; nylon plates are gentler and daily-friendly; rock plates are trail armor.
- Sizing
- Whether a model runs true, small or large versus your usual size. Leave a thumbnail of space at the toe, and size for your feet at mile 18, not mile 1.
- Durability
- Rough outsole and midsole life in miles. Racing foams flatten around 200 mi; dense daily trainers hold up past 500 mi.
- Rocker geometry
- Rated 1–5 for how much the sole curves up at the heel and toe. A flat sole (1–2) relies on your foot to bend; an aggressive rocker (4–5) tips you forward automatically, which saves the calf and forefoot on long efforts but can feel unstable at slow speeds.
- Energy return
- Rated 1–5 for how much of each footstrike the midsole gives back. Old EVA absorbs and stays absorbed; supercritical foams like ZoomX, PWRRUN PB and Lightstrike Pro rebound hard. High return feels lively and reduces fatigue, but tall bouncy foam is less stable.
- Stability
- Rated 1–5 for how much the shoe guides your foot through the gait cycle. Lower numbers mean a neutral, free-moving platform; higher numbers mean firmer medial posts, guide rails, or a wider base to slow excess pronation.
- Responsiveness
- How quickly the shoe snaps back and gets you into the next stride. It blends energy return with firmness, plate stiffness and rocker: soft, slow-recovering foam feels muted and dead underfoot, while a firm supercritical midsole under a stiff plate feels sharp and eager. High responsiveness rewards faster paces; low responsiveness is calmer and easier on tired legs during recovery miles.
- Traction
- How well the outsole grips the surface underfoot. Road traction depends on rubber compound and siping; trail traction depends on lug depth, spacing, and pattern. Deep, widely spaced lugs bite mud and loose dirt, while flatter soles feel faster on hardpack.
- Purpose
- Race day, tempo, long training runs, daily miles, recovery or trail. Most runners are best served by two or three shoes covering distinct purposes.