First, remember that no implant will handle every type of system. i.e. your gym may use an access control that is not compatible with the flexDF, but may be compatible with the xEM. But your work cards may use a different tech than your gym,. Or it may not be compatible with any implant.
If you have an access card for your gym or work, try scanning it with an NFC app like NFC tools. Also buy the DT diagnostic card. I always have it on me. You can hold this up to the readers and it will tell you what frequency they use, which will narrow down what implants might be compatible. The flexDF and the Vivokey are both high frequency. Many access control systems use low frequency.
Definitely read this before you buy anything or you may get an implant that won’t work for what you want. Chip compatibility with systems and devices