Good question! The relevant rule here is <R6d>:
(emphasis mine)
“VEX brand rubber bands” are repackaged Alliance non-latex, so, reading things literally, no, rubber bands made from other materials would not be legal.
But, a Q&A entry from Nothing But Net ruled that rubber bands made from other materials were OK as long as they were “close in elasticity”.
But but, a more recent Q&A entry, this one from Turning Point, suggests that rubber bands do need to be made from the same material.
(Note that previous season’s Q&A rulings do not automatically carry over.)
But the real point here is that last sentence in <R6d>:
It is up to inspectors to determine whether a component is “identical” to an official VEX component.
If an inspector really wanted to, they could perform some sort of “elasticity testing” on your rubber bands, and if they determine that their elasticity is substantially different from the VEX bands, they could potentially fail your robot for that reason. But I’ve never heard of anyone doing anything like that, and think it’s pretty unlikely that anyone ever would. In pretty much all cases, the inspectors’ procedure for determining whether your rubber bands are “identical to legal VEX parts” (if they perform such a check at all) will consist only of checking their size.
So, two takeaways:
- Practically speaking, can you use rubber bands made from different materials than the VEX bands? Yes, teams do it all the time.
- If you’re at all worried about the material your rubber bands are made from, save yourself the trouble and buy a 1lb box of Alliance Non-Latex #64 rubber bands (less than $5 on Amazon for multiple seasons’ worth).