Two CNC-machined aluminum rectangle blocks, sized and interfaced to combine with every other block in the X-Blocks system. Stack them with the Large X-Block or Triangle "Y" Blocks to build custom part-support and hand-rest configurations, or use them on their own the way you'd use a traditional 1-2-3 block — with the added benefit of interlocking feature and full compatibility with the rest of the system.
Pairs with the 2,4,6 X-Block and Angle "V" Blocks to expand your configuration options.