Wheel diameters are given in inches, since this seems to be the common consensus for wheel and tire sizes for whatever reason (blame the imperial system).
Weight shown is the weight per wheel. Offset is measured from the outer edge of the wheel to the mounting surface where the hex adapter sits, so the more positive the offset, the more the wheel will stick out and make your build wider. Conversely, negative offset tucks the wheels inward for a narrower stance. Price is always for a four-pack unless stated otherwise.
Heavier wheels are a great and cheap way to add some more weight to your crawler and move the center of gravity lower. This improves stability on steep inclines and reduces the likelihood of rollovers when traversing obstacles. The added rotational mass can also help maintain momentum through technical sections, though it will slightly reduce acceleration and put more load on your steering servo.
