A radio frequency identification RFID device (100, 200,300,400, 600) and a method of making the RFID tag are disclosed. The RFID device is suitable to be attached to an object and to be tuned at assembly time to material surrounding the device and comprises a wireless communication device (101 201, 301, 401), such as an RFID chip or strap and an antenna structure (102, 202, 302, 402, 602). The communication device has at least a pair of contact points (221, 521). The antenna structure has a sheet (103, 203, 303, 403, 503, 603) of electrically conductive material being provided with an inner opening (104, 204, 304, 404, 604) so as to provide a hole through the antenna structure. The inner opening is configured to facilitate a locking mechanism engaging with the tag through the opening and the sheet is further being provided with an elongated slot (105, 205, 305, 405) with a first and a second side. The slot has an inner end (106, 206, 306, 406) at a periphery of the inner opening and an outer end (107, 207, 307, 407) at a periphery of the sheet. The slot is formed so as to provide a spacing between the first side and the second side. The conductive material is electrically connected from the first side of the slot to the second side of the slot via the contact points of the communication device and through the communication device at a position between the inner end and the outer end. The position is determined so as to tune the RFID device to a pre-determined resonance frequency allowing the device to be adapted to specific electronic parameters and tuned to different configurations depending on the materials directly surrounding device.
