Patent ID: 8535297

Claim:
A treatment instrument for an endoscope, the treatment instrument comprising: a coil-shaped tubular body that is configured to be inserted through a curvable treatment instrument insertion channel of the endoscope, the coil-shaped tubular body comprising: a first coil that has a spring constant per unit length of 15 N/mm to 500 N/mm; and a second coil that has a spring constant per unit length of 15 N/mm to 500 N/mm, wherein the spring constant per unit length of the second coil differs from the spring constant per unit length of the first coil, wherein the second coil is coaxially connected with the first coil, and wherein the ratio of the spring constant per unit length of the first coil and the spring constant per unit length of the second coil is greater than 1.0 and less than or equal to 2.0.