Think reusable straws, wraps, and cups are always better for the environment? Think again.

Single-use straws and forks, plastic sandwich bags and wraps, and disposable cups can all wreak havoc on the environment. Many consumers are switching from these products to reusable alternatives with the assumption that these products are have less environmental impact.

A new study shatters that assumption. Although they are made from more environmentally friendly materials, reusable products are not necessarily always more green since their impact depends on how they are used. Some of these products might actually be worse for the environment than disposable plastic ones, the analysis published in The International Journal of Life Cycle Assessment shows.

The climate, water, and energy footprint of reusable products depends more on how they are used—than how they are made.

“This work pursues the misperception that reusable products are always better than single-use products, no matter what,” says Shelie Miller of the University of Michigan’s School for Environment and Sustainability. “In reality, reusables are generally better than single-use products, but they actually must be reused, and often reused a large number of times, to realize their environmental benefit.”

Prachi Patel, Anthropocene