We have used the trundle beds a couple of times. The picture on allears is very helpful and I hope you found it. The resort says it is for age 9 and under. If lbs will help you .. I would say 65 - 70 lbs and under. I have two children around that ... one is 8 and one is 10... they are about the same size ... but our 10 year old will be having a growth spurt soon I hope. Anyway ... either one will still fit on the bed, but we will probably take that trundle mattress off the metal support and lay it on the floor with a sleeping bag. This may be our last time using a trundle and POR ... sniff, sniff ...