They can be installed without any problems; but the function should previously kontrollieren.Klappe and bolts are made of Einfachkunststoff.Das clack of the bolt frightens our (fearful!) cat even after months still off and we have to entice every now and then, for example, to having Thunfischteilchen (discounters can) to the animal encourage. A complaint in Germany about the function of the door was answered straightforward: We received immediately from England a new flap (kplt!). The investment in chip and flap was worth it.