In one embodiment, a surgically implantable adjustable ring comprises a ring body, which includes a closure system having first and second end parts. The ring body is designed to be closed around a tubular organ by the closure system, constricting the tubular organ by forming a loop. The first end part is shaped like a sleeve having a first and second end portions, and is designed to receive the second end part of the ring. The sleeve is substantially perpendicular to the main direction of the first end part of the ring, and the second end part of the ring includes a locking protrusion adapted to hold the sleeve in position, securing the ring in a closed position by engaging the locking protrusion in an opening disposed on the sleeve.
