U15610 93-120 CFM
U15617 273-341 CFM (~$87 on amazn)
Going the the web site are the same size and weight with the only difference being the slight color difference and CFM which is a very big difference But 4905 seems to be the one to get with best performance and price 274-374 CFM: (~$73 on amazon)
Should have asked for decibels…