A nice touch with the 6 inch square format is you can rotate tiles for visual interest.
Flooring & Tiles 1 tile, 3 mm, 30 Days, 5/16", 6 inch, 6 inch square, AHS-101, Bedroom, Chestnut, Dark, Dura Luster Urethane, Glue Down, Hardwood, Individual, Money Back, Oak, Parquet, Residential, Returns Accepted, Seller, Tongue & Grove, United States
Bruce 6″Sq X5/16″ Chestnut Oak Dark Parquet 7 Finger Strip AHS-101 Wood Flooring
You will find that the 6 inch square size gives each plank a neat, balanced look on the floor.