The faster you push the harder it gets
Sleds used for working out don't usually come with wheels because they're supposed to make moving things easier. Torque USA's M series Tanks are a little different because they have wheels with adjustable resistance. Because of the wheels, it's easier to find a suitable surface to use them whether indoors of outdoors. You don't have to worry about scratching up or leaving a mark on surfaces like wood or worry about the surface scratching up the sled like when using a regular sled on pavement.
All three versions of the Tank have 3 levels of resistance: level 1 for speed, level 2 for acceleration, and level 3 for explosive power. It works in a way that the faster you push, the harder it gets. The Tank MX has an extra mode, called the MX mode, that increases the resistance of each level by 25% by flipping a lever.
The sled itself has plenty of handles and a variety of attachments for pushing and pulling. They even have wheelbarrow handles for dead lifts, shoulder shrugs, lunges, and more.