I agree with TomA, as I also chose the taller Harley sissy bar with a backrest pad that matches the OEM SGS seat. The shorter backrests look more low profile/nicer, but not nearly as functional. I've grown to like the taller backrest, and so does my lady. She's 5'8", the short backrest wasn't going to be comfortable for her.
You require:
Docking Hardware
Sissy Bar
Backrest Pad
Docking Caps - Optional
*Note, these are the parts I chose. Since I am blacking the bike out (minimal chrome), needed a taller backrest, and the pad which matches the OEM Street Glide Special seat.
Since these pictures were taken, I have added the optional magnetic caps and a black backrest pad mount. I wish you had a choice between black and chrome backrest pad mount in the box, but I guess you don't. They make the black mount optional.