Marc Francis Costanzo (born August 1, 1972) is the co-lead singer of the Canadian pop band Len. His sister Sharon, better known as Shar, also sings with him. Even though he is still with the band, in the making of a new album, he is a producer/writer as well as Senior Creative Consultant at EMI Music Publishing Canada. Costanzo spent much of 2007 in London with his sister working on various projects with his former manager Graeme Lowe. For a while, he was a guitarist for the punk Canadian band Sum 41 when they didn't have a guitarist in 1998. His affiliation with Sum 41 ended just before the release of Len's major label debut, You Can't Stop the Bum Rush. Costanzo is of half British, half Italian ethnic descent.