| 摘要 |
A sleeve includes a passage defined therethrough so as to accommodate a polygonal object. A plurality of ridges extend from an inner periphery of the passage at even spaces and grooves are defined between the ridges. Each of the grooves is a rounded groove and each ridge has two side surfaces and a top surface which is in connection with the two side surfaces. A clamp angle between two extension lines of the two side surfaces of each ridge is in a range between 40 to 60 degrees.
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