Milli provides gradual expansion from 15mm to 40mm, which is similar to the typical range of sizes in static sets. Milli may mimic the size of tampons, speculums, and possibly your partner. There are some static sets with a size slightly larger than Milli (41-42mm); however, they generally require making a larger jump in size from one to the next, which some women may find difficult. Per the British Journal of Urology the average penis diameter is 37mm, and the 40mm size replicates the majority of men.