I like the carepoint u40 syringes 29 and a half gauge. The 31 gauge works better on a human with thinner skin. I don't like the shorter needles as cats tend to have thicker skin and a higher gauge is thinner. I buy mine from ADW and they have half unit markings on them.
I also have the U100 syringes with half unit markings and a conversion chart that I use for smaller doses.