Abstract: Provided is an overtube assembly including an overtube having an adjustable length. The overtube assembly has the overtube and a mouthpiece. The overtube has a plurality of recesses (e.g., grooves) on the outer circumference thereof. The mouthpiece has a locking portion (e.g., a protrusion or ridge) that is locked to the recesses. The mouthpiece can move between a locking position at which the locking portion engages with the recess and an unlocking position at which the locking portion does not engage with the recess.

Abstract: A detachable multi-ring traction device is inserted into a body through a forceps channel of an endoscope. When a lesion mucosa in the body is resected through an operation performed outside the body, the detachable multi-ring traction device is configured to be fixed by a clip to the lesion mucosa and a normal mucosa in order to pull the lesion mucosa, the normal mucosa opposing the lesion mucosa. The detachable multi-ring traction device includes toroidal rings each including a core curve and a meridional disk, the rings being coupled to each other such that outer edges of two adjacent ones of the rings are in contact with each other and the rings are connected to each other in a diametrical direction of the core curves.