The tyre retreading process implies a few necessary steps, such as the initial inspection of the tyres, the buffing, the tread preparation and building, the enveloping, and in the end, the final inspection of the tyres. During the initial inspection, the tyre retreaders check whether the casing is acceptable for the process, by thoroughly verifying it both on the outside and on the inside. Buffing implies the preparation of the worn tread surface of the tyres for following steps, the original tread, as well as a part of the material underneath it being removed, in order to provide the casing with the required dimensions and surface texture. After that, comes the tread preparation and building, where tyre retreaders apply a pre-molded retread or a piece of new tread rubber to the casing surface that has already been buffed and prepared. Then, tyre retreaders put the tyres into an envelope, which presses the tread uniformly on the cushion and the casing, with the use of a vacuum system. During vulcanizing, heat and pressure is applied to the tyres, so that the rubber obtains the best possible physical properties and maximum adhesion to the surrounding elements. In the end, tyre retreaders do a visual final inspection of the outside and inside of the final products, ensuring that they are properly retreaded and that they meet the quality and safety standards required in the industry. Some tyre retreaders use, apart from visual inspection, an additional instrumented inspection, using specifically designed X-ray machinery, in order to ensure the products that the products they provide are of the highest quality.