There are three common resistance bands.
For the standard power resistance bands, the circumference is approx 81 inches when the band is not stretched. After being folded or crimped, the packaging volume becomes very small. The difference is that the resistance of the resistance band will change according to the different width, like 0.64cm、1.3cm、2.2cm、3.2cm、4.5cm and so on. The wider the width, the greater the resistance. Here is the link for your reference:
https://www.hq-rubber.com/product/da1-power-resistance-band
And the other popular resistance band is mini loop band. It’s portable. The standard length is 50 or 60cm, and the width is 5cm. You can choose different thicknesses, the thicker the thickness, the greater the resistance. Here is the link for your reference:
https://www.hq-rubber.com/product/mbg-anti-slip-grid-mini-loop-resistance-band
In addition, flat band have also been receiving increasing attention recently. Because of its comprehensive function, it can not only be used for fitness exercise, but also for yoga and even rehabilitation physiotherapy. The width is standard 15cm and the length can be 160cm、180cm and 200cm. The difference is also thickness. Here is also the link for your reference:
https://www.hq-rubber.com/resistance-band/flat-band