The Ei157 Pattress is designed to facilitate installation of bulky wiring and conduits. The Ei157 Pattress is designed to be used in conjunction with Ei151TL/153/154TL/156TL/156TLH Smoke and Heat Alarms. The Ei157 Pattress is designed so that any of the alarms listed above will fit on top of the Ei157 (the Ei157 is specifically designed so that such alarms will screw directly to the Ei157). The Ei157 Pattress must only be used with one of the Smoke/Heat Alarms listed above ž otherwise the unit will not comply with the mandatory safety regulations.