We recently redesigned the number four block to better fit in with the rest of the set. We'd love to help our existing fans update their sets. If you would like to replace your fours, you can get 4 new blocks for $10! Visit our shop to update your set.
The SumBlox design is based on the fact that each number is representative of its value in respect to the other number blocks. Our earlier four design wouldn't stand up on its own, and needed to be joined with the six to really demonstrate its true value.
The new iteration is a much more accurate version. The perfect solid wood number block to integrate with the rest of the set and encourage new adventures through open ended and explorative play!