It is a bit smaller than you would think from the picture, but the product information does include the following:

Height: 19 millimeters
Width: 13 millimeters
Length: 18 inches

I got this for my mother for Christmas. She at first thought the chain would be too short, but it comes down a bit (maybe 1-2 inches) past the collarbone and looks very nice on her. It's dainty and pretty and does sparkle for its size. Nice gift.