Abstract: A belt formed of elastomeric material is provided for transmission of forces in cooperation with at least two pulleys. The belt is formed by an outer part under traction, an inner part under compression and an intermediate part interposed between the inner and outer parts. The inner part includes at least two lateral, opposite and convergent surfaces suitable for transmitting frictional forces with the corresponding surfaces of the pulleys. The belt includes a plurality of transversely directed alternating protuerances and cavities in the inner part. The sequence of transversal cavities and protuberances define an undulated profile. The ratio between the pitch (p) and the depth (h) of the transversal cavities is between 8 and 20, and the ratio between the radius of curvature (r) of the transversal cavities and the depth (h) of the cavities is between 3 and 6.