Cucumbers should be green as yellow color indicates old age and that the seeds are hard.  Large cucumbers are more likely to have large seeds than small ones of similar color.  Reject cucumbers that are shriveled, withered, or have any signs of puffiness.  Keep cool and humid (45 to 50 degrees) and use within  a few days.

Grades

Field grown cucumbers provide for 6 grades, U.S. Fancy, U.S. Extra 1, U.S.1, U.S.1 Small, U.S.1 Large, and U.S.2.

U.S.1 fairly well colored, fairly well formed, not over grown and which are fresh, firm, free from decay, yellowing sun burn, bruising, scars, freezing, dirt, or damage from insects or mechanical means.  Unless otherwise specified, the maximum diameter of each cucumber shall not be more than 2 3/8 inches and the length of each cucumber shall not be less than 6 inches.

U.S.1 Small  consists of cucumbers which meet all requirements for the U.S. 1 grade except for size.  Each cucumber shall not be less than 1 1/2 inches or more than 2 inches in diameter.  There are no requirements for length.

U.S.1 Large  meet all requirements of  U.S.1 grade except for the size.  The minimum diameter of each cucumber shall not be less than 2 1/4 inches and unless otherwise specified, the length of each cucumber shall not be less than 6 inches. There is no maximum diameter and length requirements.