? What syringe needle LENGTH do you use?

Giving River her Lantus via U-100 syringes with 8mm needles.
When she got her B12 supplement, the vet gave us a few with 12.7mm needles that felt so much more…substantial going into her skin.
What do you use? Should I try to seek out longer needle length for everyday insulin? (Also, can we talk about how irritating it is that even syringes are controlled in so many U.S. states?)

 

This is what I was using for Sketch and seemed to work well.....8mm ultra fine:

BD U-100 Insulin Syringes 31g 8mm 3/10cc 1/2 unit markings 100/bx

 

I've always used 1/2 inch but always on long hair cats and never a scruff shot. They can look like a sabre when you first see one but it made our lives a lot easier, I cannot even remember dealing with a fur shot.
Apparently these are slowly being phased out for human use which is 99% of the industry. Some nurses I've talked to have never seen one.

 

I use 1/2 inch needles on Teasel. He's a short haired kitty with very loose skin. They work well for me when I give his shot in the flanks. I don't use his scruff.

 

See also this thread about syringes.