Good morning!
The webbing strap you see clipped on his belt is called a "Karabinerschlaufe". It was a short cloth (early versions were made of leather) strap that was used to pull the fuse on handgrenades. There is a great stormtrooper instruction movie in the Bundesarchiv which features the use of this strap.
Best regards from the Netherlands,
Sven
The strap:
The instruction video: