Luer Lock or Luer Slip? Comparing Syringe Connections

4 min reading time

Luer Lock and Luer slip are the two common connection types on disposable syringes. With Luer Lock, the needle or line is screwed onto a thread; with Luer slip, it is simply pushed onto the cone. Which version fits depends on the application, the accessories already in use and how secure the connection needs to be.

Luer Lock: a threaded connection

On a Luer Lock connector, the syringe cone sits inside a collar with an internal thread. The needle, extension or line is attached and secured with a short twist. As a result, the connection cannot come loose unintentionally, even when the system is under tension or pressure.

This is why Luer Lock is often chosen when syringes are combined with infusion lines, three-way stopcocks, extension lines or syringe pumps. You will find matching accessories under Infusion sets and accessories. For syringe pumps, the pump manufacturer usually specifies which syringe types and sizes are approved. Have this list at hand before ordering so that only compatible syringes are purchased.

Luer slip: a push-on connection

The Luer slip connector is a plain push-fit cone without a thread. The needle is pushed on and held in place by friction between the two conical surfaces. Connecting and changing needles is quick, which is valued in many routine applications in practices and on wards.

Luer slip syringes are the standard version in many product ranges and are available in all common volumes; you will find a selection under Disposable syringes. Both systems are based on the standardised Luer cone with a 6 % taper. Syringes and needles from different manufacturers are therefore generally compatible.

Luer Lock and Luer slip compared

Feature	Luer Lock	Luer slip
Connection	screwed on via a thread	pushed on, held by friction
Security of the connection	protected against unintentional loosening	depends on how firmly the cone is seated
Changing the needle	twist required	quick push on and pull off
Typical accessories	three-way stopcocks, extensions, syringe pumps	disposable needles for routine use
Name in catalogues	"Luer Lock", "LL"	"Luer", "Luer slip"

A needle with a Luer hub can generally be attached to both a Luer Lock syringe and a Luer slip syringe. However, the connection is only secured against loosening if both sides have a matching thread.

Concentric or eccentric tip, two-part or three-part

Regardless of the connector, the cone is either centred (concentric) or offset to the side (eccentric). An eccentric tip makes it easier to position the needle flat, for example in applications close to the surface. Many manufacturers produce small volumes with a concentric tip and larger volumes with an eccentric tip. The product data sheet is always decisive.

Syringes are also divided into two-part syringes, made of barrel and plunger, and three-part syringes with an additional rubber stopper on the plunger that provides an even gliding resistance. Many facilities define the preferred design in their standard product list. You select the matching needle by outer diameter and length; our article Needle sizes and colour code gives an overview. Disposable needles are available in the Needles category.

Standards: ISO 80369-7 and protection against misconnections

Dimensions and requirements for Luer connectors used in intravascular and hypodermic applications are specified in ISO 80369-7. This standard replaced the earlier ISO 594-1 and ISO 594-2. The entire ISO 80369 series pursues one overarching goal: connectors from different application areas should not be able to connect to each other by mistake.

For enteral applications there is therefore the ENFit connector according to ISO 80369-3, and for neuraxial applications the NRFit connector according to ISO 80369-6. Both are deliberately incompatible with Luer. For purchasing, this means that syringes for these areas are separate items and should be stocked and ordered separately from Luer syringes.

Checklist for purchasing syringes

Define the connection type: Luer Lock or Luer slip, matching the needles, lines and stopcocks in stock.
Check the tip position: concentric or eccentric, depending on volume and application.
Clarify the design: two-part or three-part.
Match volume and graduation, for example 2 ml, 5 ml, 10 ml or 20 ml.
Observe approvals: for syringe pumps, the pump manufacturer's list.
Check product details: sterility, CE marking, expiry date, manufacturer and item number.
Compare packaging units: each supplier sets its own pack size and price.

Related categories

Frequently asked questions

What is the difference between Luer Lock and Luer slip?

With Luer Lock, the needle is screwed onto a thread and secured against unintentional loosening. With Luer slip, it is simply pushed on. Both use the standardised Luer cone.

Do needles fit both Luer Lock and Luer slip syringes?

Generally yes, because both systems are based on the same cone. However, the connection is only secured against loosening if both sides have a Luer Lock thread.

Which standard applies to Luer connectors?

Luer connectors for intravascular and hypodermic applications are described in ISO 80369-7. The standard replaced ISO 594-1 and ISO 594-2.

What does eccentric tip mean?

The cone is offset to the side instead of centred. This makes it easier to position the needle flat in certain applications.

Are ENFit syringes compatible with Luer?

No. ENFit connectors for enteral applications are deliberately designed according to ISO 80369-3 so that they do not fit Luer connectors.

Disposable syringes with Luer Lock and Luer slip connectors from various manufacturers are available in the Syringes and injection category. Looking for a specific item that is not yet listed? Send us a product request.