These are two 3D models that have been drawn based on a well-known surface which mathematicians call the ‘Mobius strip’.
We generated the Mobius strip surface in MathMod software (former K3DSurf software), although you can easily draw it in almost any 3D software. Then we modeled both 3D models in Blender 3D software. The red 3D model is a Mobius strip surface that was added thickness, and the green 3D model was obtained by deleting certain faces on the 3D model. Of course, both 3D models are very easy to draw; if you still need help drawing them yourselves, the Internet is full of tutorials not only for drawing the Mobius strip surface but also 3D models like this one painted in green. If you do not want to waste your time drawing a Mobius strip, on the Mobius Surface link you can download one that we have generated in MathMod software for you.
K3DSurf + Rhino 3D + T-splines plug-in
Surface 3D model - .igs (Initial Graphics Exchange Specification)
.obj
Geometry: Mesh - Quads only (Low poly 3D model); Mesh topology supports multiple subdivisions; 3D models without texture and materials