A system for holding in a conduit (7) cables and/or ducts with different diameters, comprising a plurality of rubbery or rubberlike sleeves (1) for inserting in such a conduit (7), the plurality of sleeves (1) comprising a number of units (2) of bonded sleeves (1) which are oriented parallel to each other, wherein within each unit (2) the sleeves (1) have corresponding outer dimensions, and wherein at least one unit (2) has a sleeve (1) having an inner diameter which differs from an inner diameter of a sleeve (1) of at least one other unit (2) of the number of units, wherein the number of the units (2) and the dimensions of the units (2) are such that therewith a stack of units can be made, in the stack of units (2) each sleeve (1) is also oriented parallel to any of the other sleeves (1), the stack of units having a rectangular shape of which each side is in detail shaped by the presence of a number of the sleeves (1) and of which each edge is in detail shaped by the presence of one, two or three of the sleeves (1).