How APC APCRBC124 UPS Battery Cartridge for APC – BR1200GI, BR1500GI looks inside?

Battery Cartridge is covered with a sticky plastic plate glued on both sides.

Stickers are strong enough to keep the battery cartridge intact. One Green and one Red showing a direction of a connecting plug.

After taking out stickers:

We can see a holder that can be disconnected and two 12V batteries:

The battery used here was: LONG WP9-12SHR 12V 9Ah
Rechargeable Sealed Lead-Acid Battery
DC power, Constant voltage charge

Holder looks like his:

Assume it is simple to replace batteries with new ones that would fit specifications of APC battery. Possibly it is also a way to restore old batteries?