a) Cross-sections: 4x6 to 10x10 (larger cross-sections up to 18x18 are sometimes available, depending on length and quality needed); b) Lengths: to 16' (longer timbers are often available); c) Target Dimensions: Circle-sawn timbers are generally targeted at 1/2" nominal dimensions; d) Tolerances: +/- 1/4". As timbers air dry, they tend to shrink somewhat, resulting in dimensions become somewhat more nominal.