nexus and cure bolt
cure bolt has worked well for me, and nexus bolt has been specifically designed to deliver air around the whole diameter of the paintball where as the stock bolt delivers it to the center of the paintball which stops breaks. my friend cliffie use's nexus bolt and not known him to have a break as yet
def go for nexus or a cure bolt there is a cure bolt 2, however not used a cure bolt 2 so cant comment on them