In a yarn feeding device (F), particularly for a jet weaving machine, and comprising a housing (H), a stationary storage body (B) of variable outer diameter, and a stopping device casing (C) which is mounted at the housing (H) for adjusting movements substantially radially to the axis of the storage body (B), the stopping device casing (C) and the mounting region (M) having aligned openings for cabling/tubing, a sealing assembly (S) is provided between the stopping device casing (C) and the mounting region (M), the sealing assembly allowing the adjustment movement of the stopping device casing (C) and maintains a communication between the openings in each selected adjustment position but is sealing this region such that no opening can form in any position of the casing.