Haven't used that, but it appears to be given under the skin, rather than into a muscle. For that, in the abdomen, 1/2 to 3/4 would be fine, and I thing that 1 1/2 inch would be a bit much. For insulin, I use needles that are about 1/4 inch, just enough to go under the skin. We do b-12 injections with 1" needles into the muscle. I don't like anything smaller that about 29 gauge needles, but longer needles have to be longer.
Noel and Betty Johnson (and Harry)2005 GulfStream Ultra Supreme, 1 Old grouch, 1 wonderful wife, and two silly poodles.