Contactless data carrier

A contactless data carrier, comprising:

• a base, which is detachably tucked into a receiving portion of an object connection device, wherein the base has a top and a bottom, which are opposite to each other;
• a plurality of annular projections is formed on an outer peripheral surface of the base, and the annular projections are arranged at regular intervals in a direction from the top toward the bottom;
• an outer peripheral surface of each of the annular projections is detachably abutted against an inner surface of the receiving portion;
• and
• a tag member, which is disposed at the base, wherein the tag member is stored with a piece of data relative to the object connection device;
• the tag member is readable in a contactless manner by a reading device;
• wherein each of the annular projections is a continuous ring and has a lower section;
• a width of the lower section of at least one of the annular projections decreases gradually in a direction toward the bottom of the base.