KARACHI, Dec 21 (Reuters) - The Karachi Cotton Association on Monday 21 December fixed the official spot rate, or base price, for Grade 3 cotton at 4,689 rupees per maund (40 kg).

The Grade 3 cotton has a staple length of 1-1/16" (inches) and micronaire value between 3.8 to 4.9 NCL (no control limits) which represents fine to coarse classes of cotton varieties.

In the kerb market the key crop varieties traded in the range of 4,300 to 4,500 rupee per maund.

Following are the grade and staple margins for the period Dec 15 to 30.