Card Number Designation Question

[Auxxiliary]

I was looking around today for a graphics card and I stumbled on 3 of the same cards but they have slightly different number designations which im not familiar with.
I was wondering if anyone could shed some light on what are the differences in the 3 cards and if there is a easy way to tell what some of the letters/numbers combinations mean.
I tried researching it but i couldnt really come up with anything. Im assuming its the chipset/compatability with motherboard, i.e. one has a "4L", the other 2 are "5L" and "2SR". One says Tri-X, i can understand if some of that is just marketing mumbo jumbo.
Are they core clock speeds, and does it have an effect that i would recognize.
Im sort of a noob at this now since i havent shopped for one in a long time so explain it like im 5 if need be.
Any help would be fantastic.
1. http://www.newegg.com/Product/Product.aspx?Item=N82E16814202126&cm_re=Radeon_R9_280X-_-14-202-126-_-Product
2. http://www.newegg.com/Product/Product.aspx?Item=N82E16814202125&cm_re=Radeon_R9_280X-_-14-202-125-_-Product
3. http://www.newegg.com/Product/Product.aspx?Item=N82E16814202123&cm_re=Radeon_R9_280X-_-14-202-123-_-Product
Thanks in Advance

 

[PP Mguire]

Differences in factory overclocked speeds. The designation is probably internal for what bios the card uses for that factory OC speed.