I got 10 of the #5 at Lowe's today for $2.60. I put one in the reosmod soft bottles. Worked like a charm.
I was off a bit.I think i seen someone mention a #6 worked,the ones i have are #5 which are 3/8" od x 1/4" id x 1/16 thick.I got a pack of 10 from Lowes for like $2 or so.They work very well,they fit up inside the top of the cap,and make a good seal against the bottle,which provides the good leak free seal that a $6 bottle should of had in the first place.In the mean time though,the Mr Clean mops are very absorbent haha.