The Carlisle Brass WF12 bulb end window stay is principally used with the bulb end casement window fastener to achieve a consistent style. However, it can be used with any one of the casement fasteners we sell. The bulb end fastener & stay are often referred to as the pear drop fastener & stay. Window Stay Sash Length Generally, to select the length of a window stay which will be appropriate for your window, you should calculate around 50-60% of the casement width. The length of the stay will determine the degree of opening, &, of course, personal preference is al...