Tdap prefilled syringes

Does anyone have info on these? Our facility uses them but they look odd with a rubber plunger thing at the end. I have not done one yet, I was told the needle is inside? Does this sound right? I think it is called Boostrix.
I worked in a physicians office and she had these. THe needles usually come separately and you attach them (luer lock type) Just twist the needle on and inject. Really easy and convenient.

No needle inside. Just pop the rubber stopper off, twist on the needle and administer. I think they advise to use with caution in people with latex allergies because of the rubber part, but I think this is an extreme precaution.

Our Td (no "ap") comes in prefilled syringe, no needle in the package--we have to attach one. Out Tdap comes in a vial and has to be "pulled up."