What is the 4 digit extension on my zip code?

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Tags

1. #specific
2. #within
3. #represents
4. #indicate
5. #delivery
6. #complete
7. #digit
8. #destination
9. #office
10. #first
11. #overall
12. #consists
13. #effectively
14. #sorting
15. #route
16. #digits
17. #parts
18. #assist