Abstract: A band slitting installation including a tensioning device allowing braking simultaneously and without friction an assembly of bands which are presented for being wound on the same drum, wherein the necessary braking effort is transmitted to two endless belt webs between which pass the slitted bands so that the belts can move at different speeds, respectively equal to the speeds of the slitted bands to the braked, characterized in that the braking efforts are on the one hand applied directly on the belts of the upper web via an upper clamping plate and on the other hand, on the lower web via a lower clamping plate made of a plurality of tubes the number and the upper surface of which are identical to those of the belts, whereby the tubes are covered with a wear resisting sheet of great hardness, transmitting the braking effort to the belts of the lower web.