This Secondary 1 lesson is an extension of volume of prisms from Primary grades. In this teaching experiment, we focus on students’ common misconception of thinking slant sides as the height of the prism. Our objective was to design a group activity with 3D Printing Pens which foster discussion to help students visualise the relationship of volume of right and oblique prism: Under the shearing principals, the volume of these two prisms with equal base area and height should stay the same. During the lesson, students experimented and explored the characteristics of oblique prisms, and they compared the volume of right prisms using their constructions to arrive at the conclusion that the right prisms and oblique prisms have the same volume.