Continuity mistake: When Summer is singing in the park, her hair changes from in front of her shoulder to behind her shoulder in between shots.
Continuity mistake: While out to dinner with William, Summer has her wine glass in her hand one minute, and when the shot changes her hands are under the table - too quickly for her to have put the wine down.
Continuity mistake: In the scene where April and Will are having the smoking contest outside of the bodega, the hand that April is using to hold her cigarette changes several times from shot to shot.
Chosen answer: The closest thing to them available in reality appears to be these: http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/press_releases__07.01.2008.