You wanna know what comes between you and your Calvins? Radiation!

Belly Armor — which claims its products protect pregnant women from harmful rays emitted by laptops and other gadgets — is pitching a product to men concerned about the effects of cellphone radiation on their fertility.

The Manhattan company branched into the menswear department this month with RadiaShield boxer briefs, which promise “to protect men’s reproductive organs and maintain fertility health.”

The high-tech skivvies, which go on sale Thursday, come with a thin layer of aluminum-like silver in the crotch area to shield little swimmers, the company claims on its site.

Co-founders Aileeen Chen and Michael Lam developed the undergarments in response to a 2007 study by the American Society of Reproductive Medicine that showed use of cellphones decreases semen quality, said spokeswoman Katherine Niefeld.

Men haven’t been asking for protection — that is, against radio waves — down there because they don’t know they need it, she added.

“If you’re a guy, how are you going to know that putting your cellphone in your pocket will do things to your sperm,” Niefeld said.

So far, health studies on the low levels of radiation emitted by mobile devices have been inconclusive, but that hasn’t stopped Belly Armor from rolling out radiation-shielding gear.

Of course, protecting the nether region comes at a price. RadiaShield boxers cost $49 a pop.