its depend on ur laptop..sum laptop got grill at back for hot air blow from ur proc cooler..so in this case for me its wub b nice u blow ur laptop cooler fan to ur proc coz the hot air will blow out tru back grill at laptop..but if ur laptop doesnt hv exhausted air to out..its more good for me make it sucking out air rather than blow in..coz the hot air cant out from ur lappy