If you’re looking at semi-trucks that are available for sale, you first need to know what they are. Semi-trucks, also known as “semis,” are hybrid tractor units and semi-trailers that help carry freight. A semi-truck is an actual truck which contains an engine and can run on its own without a trailer as well.

Fuel-efficient and aerodynamic, today’s semi-trucks are Freightliners of the future, complete with features such as high-tech, space-age cabins, and active grille shutters. Listed below are some of the best semi-trucks available for sale in the country today:

• Freightliner Cascadia® Evolution: The Freightliner Cascadia® Evolution is setting the industry benchmark for long-haul, fuel-efficient application.

It is the flagship model from the stable of Freightliner. The semi-truck is setting new standards with its state-of-the-art technology, ease of maintenance, innovative design, and fuel economy (7% increase over the original model). The semi hit a mileage of 9.31 mpg with a full load in real-world conditions on a cross-country excursion. This semi’s remote diagnostic system eliminates guesswork from the equation. The cab layout is ergonomic and easy-to-use, the semi has steering-wheel-mounted controls, and the message center assists drivers in focusing on the road ahead.

Kenworth T680 Advantage: The Kenworth T680 Advantage features a 10-speed automated transmission and an optimized powertrain, along with fuel-efficient Meritor MT40-14X drive axles.

The semi truck also has new aerodynamic elements which enhance its fuel economy. Other notable fuel-efficiency features include driver performance assistant and predictive cruise control. The 52-inch semi-truck is especially useful for regional hauling applications as it provides a great working and living environment for drivers. It comes with LED interior lighting, easy-to-use driver performance center, an ergonomic dashboard, air-assisted hydraulic clutch, and adjustable advanced suspension seats with climate control.

International ProStar® ES: The ProStar® ES features a fuel-efficiency package which makes it more efficient than its predecessor. It also boasts of the perfect balance between drivetrain optimization and superior aerodynamics. The ProStar® ES bundles a drivetrain that employs advanced down-speeding with fuel-efficient rear axles and an aerodynamic body. The Cummins and Eaton® SmartAdvantage™ powertrain powers this semi-truck. It also features several other customizable adjustments such as full-length chassis skirts, contributing to 11% better fuel economy, thus making each mile count.

Kenworth W900 A & B: The first (A) and second-generation (B) of the Kenworth W900 series are two of the best classic semi-trucks on the road right now. The Kenworth W900A is a smooth-driving and quiet truck with smooth suspensions. With no rattles and wind leaks, the semi-truck is a quality purchase. Moreover, it has a high resale value as well. The Kenworth W900B has a long, fiberglass hood and a classic design, complete with V.I.P. interiors, a well-insulated, well-designed and quiet cab, excellent ventilation, bright interiors, and convenient exterior access to the bunk area.

Before picking one of these semi-trucks that are available for sale, you need to check their features carefully to find one that’s the best fit for your requirements.