@ErniePantuso
In your case (EAP225 V2), any 802.3af-compliant injector should do. However, the "TL-POE170S is incompatible with EAP235, EAP225, and EAP225-Outdoor. To power up these EAPs, TL-POE160S is recommended to use." (source).
TP-Link has a FAQ which also discusses cable length here: https://www.tp-link.com/no/support/faq/906/ - as long as you use good quality copper cabling, you should be fine.
However (and this is also mentioned in the linked FAQ), this does not apply to TP-Link EAPs that come with a passive PoE injector (such as the EAP225 V3) - while it says they are 802.3af-compliant, they only accept one of two possible PoE wiring pinouts (mode B according to the FAQ). PoE power sourcing equipment (PSE) such as an injector or a PoE switch can be either mode A or mode B (or have different pinouts on different ports), and powered devices (PD) must accept both pinouts according to the standard. However this is not the case for "hybrid" devices from TP-Link (and other suppliers) - so you need to make sure your power sourcing equipment provides the required mode. Don't ask how I found out about the different modes :).