Koa is similar to diamonds. There are different grades that reflect the quality and attractiveness of the wood. The predominant factor considered when grading Koa is the presence of curl. Even though Koa can range from light golden colors to darker chocolate browns, color is not typically considered when grading except where significant mineral staining or similar defects are present.
High curl sets have bold, tight curls prevalent throughout the entire piece with very few, if any, imperfections. Some high curl sets have a strong curl throughout most of the piece with very limited, if any, areas where curl fades.
Medium curl sets have strong curl in some areas although curl visibility may be limited at specific angles. While medium curl sets have far less figure than highly curly pieces, they are much less expensive and therefor make a great option for beginner luthiers looking to build a beautiful ukulele at an affordable price.
Select/Better sets are templated with wood that is quater-sawn, but there is very little, if any, curl throughout each piece. The select/better sets are the most affordable grade and are therefore a good choice for brand new luthiers who are looking to practice building ukuleles.