Cisco Estimate question

When speccing something like a 4500X. There are mulitple different software options such as

45XUK9-39E

CAT4500-X Universal Crypto Image

28 days0.00S45XU-39E

CAT4500-X Universal Image

28 days0.00S45XUK9-38E

CAT4500-X Universal Crypto Image

28 days0.00S45XU-38E

CAT4500-X Universal Image

28 days0.00S45XUK9-37E

CAT4500-X Universal Crypto Image

28 days0.00S45XU-37E

CAT4500-X Universal Image

28 days0.00S45XUK9-36E

CAT4500-X Universal Crypto Image

28 days0.00S45XU-36E

CAT4500-X Universal Image

28 days0.00S45XUK9-34-1512SG

CAT4500-X Universal Crypto Image

28 days0.00S45XU-331-1511SG

CAT4500-X Universal Image

28 days0.00S45XUK9-310E

Where can I find out what the difference is and which to choose. I will be using a VAR but I'd like to learn myself