One of the most controversial and in my opinion the most rewarding tuning products are latex hoses. Even in the age of tubeless tires, these in combination with fast folding tires guarantee minimal rolling resistance. Compared to their butyl brothers, you can save two to three watts of power loss per wheel (!) at 30 km/h. At higher speeds even more, the rolling resistance increases linearly.
I like to use the models from Vittoria from Thailand. They are leaders in latex processing. In my shop there is the variant in the medium width for 25 to 28 millimeter tires (700C/28 inches) and with a 48 millimeter long Presta valve, which you can also unscrew to extend it. Warning: this valve is already too long for a few discs!
You can find out how best to proceed with the assembly so that they don't collapse here at with in the time trial hacks . However, I do not give any guarantees. And: because latex reacts like raw eggs, it's really only for competition use and not for regular conversion. The tubes like to take on the shape of the rim base and the inside of the tire and are then at most still safe enough for training.