Bells 2-1/2" - Our basic Aluminum Finished Home Door Bell looks great anywhere.Bells 2-1/2" features include: Satin Aluminum Finished Home Door Bell With Snap-On Cover For Easy Installation May Be Operated By 6 VDC or 8-16 VAC Transformer Order Qty of 1 = 1 Piece Below is more info on our Bells 2-1/