Hi! I don't have any experience with the REI kits, but it's hard to go wrong by starting with any good small basic kit like the Red Cross personal kit and making those changes that experience suggests are appropriate for where you're going to be hiking. For example, this time of year in my area I'll load up on insect repellant wipes and sting/itch relief wipes in the small individual packs.

I'm not the world's biggest fan of the Red Cross and their marketing arm, but their kits are a good starting point. As I say, I can't speak from personal knowledge about REI's.

If you want something smaller but still functional, IMHO you're better off designing your own (assuming you've had at least a basic first aid course; if not, stick with the commercial kits or, better yet, take the course). I have Sucrets throat lozenge tin that I have packed with an assortment of bandages, wipes, ointments, etc., that I find easy to shove in a pocket and take with me when going ultra light is the goal.