Schluter Systems Rondec L Sand Pebble PVC Inside Corner Tile Edge 12 Pack

These are genuine Kerdi products. The I/PRO100SP is a prefabricated corner for Rondec that eliminates the need for a mitered edge. It is used to create 90 degree inside corners. The I/PRO100SP corner is designed for use with the PRO100SP profile.

eBay