I guess an "other" box would be more specific, but it might be hard to search by that criteria.
Current Choice
Under 1"
1"-2"
3"-4"
5"-6"
7"-12"
Over 12"
Suggested Choice, since there are a large number
Under 1"
1"
1.5"
2"
2.5"
3"
3.5"
4"
4.5"
5"
5.5"
6"
6.5"
7"-12"
Over 12"