This bundle includes two 8-pin and two 6-pin single row headers with 15mm long leads that make it perfect for use with Arduino Shields, and they're stackable. This header bundle is compatible with all versions of Arduino Uno, but you may have noticed the R3 has a few additional pins so we created a header bundle for the Uno R3 (P/N: 2261343) that includes (1) 6-position, (2) 8-position and (1) 10-position header. They are also available separately.