Size 30 Snaplock bags filled with water & frozen are good for 2 or 3 days.I don't bother my bait(skippy)is thawed before I go ,keeping it out of the wind helps though.Normally take 2 ,1 I'm using the other in a clean sack inside a normal sack.The white outer reflects heat well & keeps the bait cool enough.Putting the catch into the clean sack stops it drying out & keeps it in good condition too.