These diagrams highlights some of the features of a wingsuit which improve its flying ability, and also highlight a few extra tools such as a knife, helmet and altimeter. The suit on the left, which appears to be a Birdman GTI, is now considered to be a small suit good for flocking and acrobatics. The suit to the right, a Tony Suits X-bird is one of the largest suits on the market, as can be seen from its protruding tail wing (beyond the feet) and large surface area on the arm wings. Such suits are capable of achieving a sustained glide-ratio of over 4:1 (4m forward for each 1m down) in a 1km vertical window.
Some features such as the pressurised back, pressurised cells and angled leading edge on the arms have large effects on the airfoil around the skydiver; imagine images of a Formula 1 car in a wind tunnel where the shape of the wings affect its down-force and aerodynamics, and apply the same image to the air passing over a wingsuit. Other features such as arm grippers and access zips are used for comfort but add little performance to the suit. It is worth noting however; that the biggest influence on the performance of a suit is the technique of the pilot, followed by his/her mass. A pilot with a relaxed technique and a good understanding of attack-angles (imagine a bird of prey building up speed in a dive in order to be able to pull out and glide), and who is light, slim and tall will have a distinct aerodynamic advantage over less well-matched pilots in performance flight.