Basically, you can choose between regular underwear or underwear specifically designed for packing. With regular underwear though, you just need something that is going to fit tightly enough that the packer will not fall out, but note that if you are likely to pull down your pants in a public restroom or while changing in the gym, packing underwear might save you some embarrassing moments. This kind of underwear uses various designs to ensure that the packer stays in the correct position, and also cannot fall out. Learn more