The difference is based on the size and the number of different ways that you can use your Transforma:
TRL24 is 24 different sizes in 1. 4 different size A-Frame ladders, 9 x step-ladder or 90° ladders, 7 x extension ladders & 4 x scaffold trestle heights
TRL35 is 35 different sizes in 1. 5 different size A-Frame ladders, 10 x step-ladder or 90° ladders, 15 x extension ladders & 5 x scaffold trestle heights.