DESCRIZIONE
The present invention relates to a downhole system for a well producing hydrocarbon-containing fluid. The downhole system comprises a casing comprising a first casing part and a second casing part, the second casing part having a casing thickness and comprising at least one sleeve having an inner face, and the second casing part being substantially a monobore in that the second casing part has an inner diameter which varies by less than twice the casing thickness; and a drop device for being immersed into the casing having at least one sleeve having an inner face. The drop device comprises a body having a width; a leading end; and a trailing end. The body further comprises an expandable sealing element arranged between the leading end and the trailing end, moving from a first position in which fluid is allowed to pass the device and a second position in which the sealing element abuts the inner face of the sleeve and seals off a first zone in the well from a second zone in the well. Furthermore, the invention relates to a downhole system and a stimulation method.