From the website:
The 21st Panzer division would be the only tank division to oppose the Allied landings in Normandy. Having been rebuilt after the defeat in Afrika the 21st was refitted with a variety of vehicles including specialist repurposed equipment, known as Becker’s Conversions (Battleground Europe page 40).
During the early part of 1944, Major Alfred Becker and his artillery command were responsible for taking obsolete captured British and French vehicles and refurbishing and redesigning them into useful machines. One such was the French UE carrier which Becker re-designed into rocket launchers mounting 28/32cm heavy rockets for infantry support. Its principal service was during 1943-45 with roughly 40 vehicles being made into this variant.