Quickly ice the sides and top of your cake using the Wilton Cake Icer Tip 789. While no coupler is needed for the Icer Tip, this oversize tip is easiest to use with a 16 in. or larger Wilton decorating bag. You'll love how easy it is to initially cover your cake with icing, and once you've covered your cake with icing using this tip, just smooth with a spatula, and then decorate or serve! This tip saves you time decorating and helps you avoid cake crumbs getting into your icing, since you cover the surface and then smooth the overlaps.