The Quantum 2 was a round-oval fit. The Quantum series was in the Arai lineup for many years, until the Quantum 2 was discontinued at the end of 2009. This was a well loved model that featured a removable head liner and cheek pads. The Quantum 2 was in production from 2004-2009. The majority of these helmets will be dated 2004-2006, with the exception being the newer graphics (Spike and Swirl colors).