If the clone is going into a rockwool or Rapid Rooter cube one that is 21/2 to 3 inches will work just fine. If going into an EZ cloner a 3-4 inch will work. The length of time from seed to when a plant will produce a nice sized clone I would say is about maybe 6 weeks or so depends on the strain you have. Ak-48 should be somewhere in that time frame.