danmdevries wrote:The needle you're looking for is called a spinal needle.
which would not be used for a run of the mill insulin injection, correct?
...In just 25 years, we have gone from using 16-mm-long(about 5/8ths long) needles that were much thicker in diameter to 4- to 8-mm needles that are very thin (and practically pain-free). But do shorter needles work as well in people with more body fat? Yes, they do. Recent studies using ultrasound to measure skin thickness at four different sites on the body showed there is minimal variation in skin thickness regardless of a person’s age, gender, race, or body mass.
Most people have a skin thickness of less than 2.8 mm, which means that even shorter 4- or 5-mm needles will penetrate the skin and reach the subcutaneous tissue.
If insulin is injected with a longer needle (over 8 mm), the chance of injecting into intramuscular tissue is greater. That causes more pain and variation in insulin uptake (and thus in blood glucose levels). The width, or gauge, of a needle has more to do with pain than does the length.
excerpt from...
http://www.diabetesforecast.org/2013/dec/do-i-need-a-longer-insulin.html