https://www.vanishpoint.com/Simple4.aspx?PageId=156
https://www.progressivemed.com/images/18870.jpg
all you do is press the button at the tip of the plunger afte finishing injecting and it retracts the needle. there are also syringes that come with a safety cover so you never have to recap the needle.
also you have to press the release button to get the needle to retract pretty hard after injecting so there is no worry of accidently retracting it while your pushing the oil in. so you never have to pull out a nother needle on your own.
I dont know if this is old news just thought id let yall know.
Cheers