For the past fifteen years, Sony's portable radios have dominated a very specific market: the federal prison. One specific model, the SRF-39FP (the 'FP' stands for 'federal prison'), remains a firm favorite 15 years after its debut. It's made out of clear plastic, allowing guards to ensure the radios aren't being used to smuggle contraband, lasts for forty hours on a single AA battery, and is rated by enthusiasts as one of the most precise portable radios around. In a New Yorker article, Joshua Hunt looks at how and why the SRF-39FP became "the iPod of prison."