Having had made me acquainted, what to look for (DIN / EN / TÜV, etc.) I have chosen for this model. 3 pieces ordered. Delivery packaged very well and within 48 hours. The installation is slightly out of hand. Smoke detectors belong to the ceiling, I have even a mounted in the kitchen, which until now no false alarms from up there, although I cook almost every day. Distributors and device - my recommendation!