More details please visit the datasheet： DH-S5500-24GF4XF-E_datasheet

Intelligent Resilient Framework 2 (IRF2)
IRF2 is the stacking technology used in conjunction with the spare ports on the panel. It offers the flexibility to stack over longer distances, such as hundreds of meters across buildings or several kilometers between sites, using long-range transceivers.
Enterprise-level Connectivity
For connectivity, fixed 1U models are offered and are ideal for branch offices or small to large enterprise environments. Each switch includes four high-speed built-in 10GbE uplinks for non-blocking transmission. PoE models can carry up to 600W to power end devices.