The study will enroll 252 MSM and 252 men who sex with women (MSW) into a double-blind, three-way randomized crossover trial with conditions of fitted, thin, and standard condoms. For MSM enrolled in the trial we will assess outcomes based on anal sex, and for MSW we will assess outcomes based on vaginal sex. The study will provide fitted condoms in 56 sizes based on combinations of length (approximately 10 mm increments) and circumference (approximately 2 mm increments), with user-determined size based on a paper template measurement instrument.