A sheath assembly for different fields of endoscopic surgery involving suction, irrigation and material removal which would on one hand enable reducing the size of keyhole to do the endoscopic surgery making it minimally invasive surgery, minimal damage to surrounding organ and practically no bleeding, faster recovery and early discharge and yet on the other hand provide for the advantages of big hole surgery. The sheath assembly of the invention would enable using variety of sheath sizes of different length and width of working sheath and thus facilitate applying to neonates as well as morbidly obese patients. The sheath assembly would enable endoscopic surgery such as percutaneous renal surgery with even about 3.0 mm inner diameter tubular sheath for large varieties of stones which would further add comfort and extra safety both for the patient as well as the surgeons.