Hardness
| VS (very soft) | 480 kg/m3 or less |
| S (soft) | 485 - 560 kg/m3 |
| F (firm) | 565 - 680 kg/m3 |
| M (moderate) | 685 - 800 kg/m3 |
| H (hard) | 805 - 960 kg/m3 |
| VH (very hard) | 965 kg/m3 or more |
Strength Groups
| S | Unseasoned - There are seven groups ranging downward from S1 to S7. |
| SD | Seasoned - There are eight groups ranging downward from SD1 to SD8. |
Joint Groups
There are six groups ranging downward from 1 to 6; they indicate mechanical properties for jointing purposes in engineering design.