Cylinder escapement The chief advantages of this escapement are: its robustness, its reliability, even despite certain flaws in its construction, its relatively low cost price and the fact that it is easy to manufacture and adjust. Its biggest drawback is that it does not provide accurate timekeeping in watches, for which it has been adapted. The cylinder escapement consists of a cylinder, hence its name, an escape wheel or cylinder wheel. The cylinder is a piece of hollow, notched steel; the edges of the notches are called lips. The first lip, the one engaging externally with the escape wheel, is known as the entry lip while the other is called the exit lip. Wedged around the cylinder shell is a piece of brass known as a "hub" on which the balance and the collet are fitted. Fitted inside the cylinder are two plugs, mounted on which are the pivots. The escape wheel has teeth which lie on a parallel plane superposing that of its base. These teeth, like those of the lever escapement wheel, are slanted so as to engage with the lips of the cylinder. The principle behind the cylinder escapement is similar to that of the lever escapement in terms of the alternating action of the escape wheel on each of the cylinder's lips. Activated by the spring, the wheel turns in the direction of the hands of a watch and the slanted tooth sends an impulse to the entry lip first, thus causing the cylinder and the balance mounted on it to rotate; this same tooth then comes to rest inside the cylinder while the cylinder itself remains in motion as a result of the build-up of speed. On its return, the slant of the same tooth engages with the exit lip, then the next tooth comes to rest against the outer wall of the cylinder. This tooth will then give an impulse to the entry lip etc. The noticeable feature of this escapement is that the wheel is in constant contact with the cylinder, and that this contact is frictional; it follows therefore that the escape wheel acts as a real brake on the movement of the balance. This is one of the main flaws of the cylinder escapement. Another major flaw lies in the fact that its swing is necessarily small.