Luer-lock is the threaded version of the standard 6% taper syringe fitting. Instead of relying on friction to hold a needle on the hub, as a luer-slip does, a collar screws down and mechanically locks the connection. The taper dimensions are standardised, so luer-lock and luer-slip components share the same conical geometry and are dimensionally compatible; only the retention mechanism differs.
Why luer-lock matters in peptide research
It is a pressure question. Any operation that builds back-pressure — pushing solution through a 0.22 µm syringe filter, transferring a viscous solution, working through a fine gauge needle — can pop a slip fitting apart and spray the contents. In a lab that means a lost sample and a contaminated bench rather than merely an inconvenience, which is why filtration steps and bulk transfers use luer-lock syringes as a matter of course.
The trade-off is that most U-100 insulin syringes have a permanently fixed needle and no interchangeable hub at all, which is what gives them their very low dead volume. Practical selection across both types is covered in the syringe and needle guide; browse syringes and vials.