Double Ended Contour Sanding Grips for Concave & Convex Profile Sanding 6 Piece Set. Large Size Grip Pads with Larger Profiles. Ideal for Crown Molding, Molding, Frames or General Woodworking Use :
Fast Mover Tools, Curved Blocks Sanding Kit, 6pcs in Case | Fast Mover Tools
Festool Interface Pad for Sanding Concave, Convex and Rounded Profiles - YouTube
FESTOOL Sanding pad R10 concave, LS130
Sanding Concave Surfaces With DIY Foam Pad/Random Orbital : 3 Steps (with Pictures) - Instructables