We recently redesigned the number four block to better fit in with the rest of the set. Unfortunately that means a lot of our earlier customers have the older four design. To thank our long time customers and make it easier for them to replace the old blocks with the new design, here you can order a set of 4 number 4 blocks for just $10!
These are the current 4 blocks, in any new set of SumBlox these will already be included. Please check the version you have before ordering replacements that may be unnecessary.