DEWALT DCF850E1 20V MAX ATOMIC impact driver kit

Torque is the twisting force the tool can apply, usually listed in in-lbs or ft-lbs. Higher figures help with large fasteners, augers and hole saws. Ratings from different makers are not always measured the same way, so treat this as a rough guide rather than a direct comparison.

Max speed is the top no-load speed, in RPM for rotating tools. No-load means the tool is running free, so speed drops once it is working. On drills, many makers list a figure per gear: high for small bits, low for control with large bits or long screws.

Tool length is the front-to-back measurement published by the maker. A shorter tool fits between studs, joists and inside cabinets more easily; standard US framing is 16 inches on center, leaving about 14-1/2 inches between studs. Check whether the figure includes the chuck or bit holder.

Brushless motors use electronic control instead of carbon brushes, which generally means less wear, less heat and more runtime per charge. Brushed motors are simpler and often cheaper, and are fine for lighter or occasional use, though their brushes can wear out over time.

This lists how many batteries come in the box, if any. Tool-only (bare) listings include no battery or charger, which suits buyers already on that battery platform. Two batteries let you charge one while working with the other.

Amp-hours (Ah) is the battery's charge capacity. At the same voltage, a higher Ah pack runs longer between charges but is usually larger and heavier. Smaller packs keep the tool lighter for overhead and light work; larger packs suit saws, grinders and other high-draw tools.

This states whether a charger is included and which type. Chargers vary in output, so the same battery can take noticeably different times to charge on different chargers. Tool-only listings usually include no charger.

The chuck holds the bit. A keyless chuck, sized by the largest shank it accepts (often 3/8 or 1/2 inch), tightens by hand and takes round or hex shanks. A 1/4-inch hex quick-change collet, used on impact drivers, takes hex-shank bits only and allows fast one-handed bit changes.

This is the maker's published warranty term. Terms for tools, batteries and chargers often differ, and some depend on registration or exclude certain uses. Read the maker's terms for what is covered, how claims are handled and whether proof of purchase is required.