The 'Bison' and 'Grille' are today's commonly used names for the German self-propelled 15cm schwere Infanteriegeschütz 33 (sIG 33) vehicles of World War II. The sIG 33 was the most powerful support weapon for the German infantry at the beginning of the war and from 1940 it was mounted on a range of tracked vehicles. This book demonstrates the construction of five 1/35-scale models of specific examples of the various self-propelled sIG 33 vehicles. The modeller is led through the various skill levels of construction by combining existing kits with some aftermarket accessories and scratch-built items.