Phillips #30 Double V Inside Corner Expansion Joint, similar in design to the #15 Double V, serves to relieve stress and control cracks at wall-to-wall junctions or where different planes abut. Expanded flanges allow for quality keying. Phillips #30 is available in 1/2″, 5/8″, 3/4″ or 7/8″ with your choice of galvanized steel or zinc.