Outpatient insulin syringes are all one piece; the needle can't be removed from the syringe. Insulin pens do have replaceable needles, which are usually 29-31 gauge.
From the blue hubs, most of the needles on the tray are 23 gauge. That's more than twice as thick, and so much better at holding on to biohazard if they are being reused.
The skeevy part is that they're all injecting at the same time. The Tranch has this communion ritual going on; it's only a matter of time before they do decide they're fluid-bonded or some other fuckery goes on. We've seen what their kitchen looks like.