SomoHapiens Mercury tips: 4.9 mm (S,M,L is dependent on the size of your ears).
However keep in mind that you have to do a little modification yourself to make it work for the isine10/isine20s.
You have to find a way to remove the plastic ring in the middle of the foam tips in order to fit onto the headphones.
Wasn't difficult for me, (I just took a pair of sewing scissors and slowly removed the glue around the plastic and the foam tips still stay in original shape. Then you can make the decision whether you want to put a little double sided tape on your isine's tip to help keep the foam tips stay there after.
My recommendation is you buy the multipack the ( 1 S, 1 M, 1L ) if you aren't sure what size will fit you, just make sure it is the 4.9mm. After you try doing the mod if you like it then buy the 3 pack for the size that you like best.
Hope this helps.