In the most common configuration of compound bows, there is a cam or wheel at the end of each limb. The shape of the cam can be different depending on the different bow designs. There are a number of different concepts of using the cams to store energy in the limbs and these can all be categorised under what is referred to and known as €bow eccentrics'. The four most common types of bow eccentrics are Single Cam, Hybrid Cam, Dual Cam and Binary Cam. That being said, there are also other less common designs, such as the Quad Cam and Hinged. The €let off' is a term that describes what occurs when the cam rolls all the way over. As these compound bows are drawn, the draw weight increases to a peak and then €lets-off' a certain percentage of the peak draw weight before a stop, which is referred to and identified as €the wall, stops the bow from being drawn further back.

The let-off is usually between sixty five percent and eighty percent of the peak weight for recently designed compound bows, although some older compound bows only gave a let-off of fifty percent and some of the most current designs give let offs of more than ninety percent. The axle attaching the limb to cam of compound bows is mounted at the edge of the cam as opposed to the centre. As the string is drawn the cam turns and provides force to compress the limb. At the start, the archer has the 'short' side of the cam, with the leverage being a mechanical disadvantage. High energy input is consequently required. When near full draw is attained, the cam has turned to its full extent, the archer has then achieved mechanical advantage and the least amount of force needs to be employed to the string to keep the limbs bent.

This is known as €let off'. The lower holding weight allows the archer to keep the bow fully drawn and take more time to aim. This €let-off' allows the archer to accurately shoot compound bows with a much higher peak draw weight than other types and makes of bows. There is a manufacturer that constructs compound bows with a ninety nine percent let-off. Even though this is unsafe, a compound bow with this degree of let off can be drawn pointed at the ground. The actual weight of the bow will keep it drawn even if the grip is released and the bow is hung by the string. Archers who perform this method of drawing the bow need to be aware of the fact that extreme caution must be exercised to avoid accidentally disturbing the bow out of the let-off zone before establishing a firm grip on the string and the fore grip.