The discrepancies between men’s and women’s beach volleyball uniforms are hard not to notice, given that women usually compete in bikinis and men play in tank tops and shorts. A question has come up in several conversations I’ve had with colleagues and friends over the past few days: Why is there such a difference in the amount of clothing these athletes wear?

The answer, according to Corinne Calabro, the communications director for USA Volleyball, is pretty simple: Because that’s what the female athletes want to compete in. Women don’t have to wear bikinis — the uniform guidelines from the Federation of International Volleyball, the governing body of all international competition, allow for many different options.

“The athletes are allowed to wear long sleeves, they’re allowed to wear shorts, tank tops,” Calabro said. “But we’ve gotten a lot of athletes on record saying they prefer to wear a two-piece because there are less places for sand to hide. They don’t view it as swim wear or anything like a fashion statement. For them, that’s their uniform.”

Kerri Walsh Jennings has been especially vocal about their decision to compete in two-pieces. She told The Huffington Post:

“When it comes to beach volleyball, we’re playing in 100-degree-plus weather. I think we’ve just gotta educate the public, take it with a grain of salt and make sure that we’re working hard and not playing up the sex appeal because it’s inherent anyway.”

The uniform guidelines for women changed in 2012. Previously, female players were required to wear bikinis when they competed. But in order to be more culturally inclusive, the FIVB changed the rules to allow for a myriad of different combinations. This year, Egypt’s team competed wearing long sleeves and pants, which was up to code with what the FIVB mandates.

Women have more options when it comes to what they compete in than men do, though both genders have to wear both tops and bottoms. When asked why men have to compete with shirts on, as opposed to in traditional men’s swimwear (which usually means going topless) Calabro said that judges need to be able to see a name and a number on each athlete’s uniform.

“It’s more for identification for the officials and to have a standard between genders,” she said.

Here are the uniform requirements for men, from the FIVB:

And here are the options for women:

Walsh Jennings and Ross worked with a designer to help come up with their own uniforms for the Rio games; Calabro said that keeping the uniforms standard between partners is the most important thing.

“Even teams of two can have different sponsors for apparel,” Calbro said. “So it’s about keeping it consistent through not just partners and countries, but all countries.”

Cold weather gear, which is what Ross and Walsh Jennings wore in their match against Switzerland on Wednesday night, is also covered by the FIVB guidelines.