From the manual .
the eclipse ego lV1 comes as standard with an eclipse shaft4 barrel.1,4
the barrel screws into the body of the ego using a right hand thread meaning that if you hold the ego lV1 pointing away from you the barrel screws into the body in a counter-clockwise direction
on the barrel back there is a 016 nbr 70 o-ring D which prevents the barrel from vibrating loose from the ego lV1 body when the marker is fired. there is also a 016 nbr 70 o-ring on the tip of the barrel back E helps with alignment when the two sections are screwed together