If you keep these in water and humidity proof ziplock bags, they are fine.  About 95% have no problem, but quality control is a bit lacking and some bad ones are inevitable at this price.  All disks are made to absorb water and expand to form a very tight bond when coated with wood glue - that's part of what makes them work.  They come in non-resealable plastic bags and are fine when they arrive but if you use some and don't put the remainder in something water tight, they will expand and become too big to fit.  That's not just these, but ALL wood disks.  It would be great if they came in resealable containers, but they don't, so have some gallon size ziplocks on hand when you open them and don't get them wet.  Great value.