From the release:
Owl Self-Propelled Gun is an resin conversion set for Imperial Guard Chimera, includes 26 resin kits and 1 metal barrel.
With this kit set, an Imperial Guard Chimera can be upgraded to:
Owl-S Self-Propelled Gun, long range artillery, great count as Imperial Guard Basilisk.
Owl-M Heavy Mortar, indirect support weapon, great cout as Imperial Guard Griffon.