The Difference Between a 2-Part and 3-Part Syringe

The Difference Between a 2-Part and 3-Part Syringe


Despite being one of the most commonly used medical and industrial instruments, syringes are often relegated to a “one-size-fits-all” designation. But there are many different syringes on the market, each designed for a specific purpose.

2-Part and 3-part disposable syringes are two of the more common syringes, both having qualities that make them ideal for a wide range of applications. Read on to learn more about these syringes and when each would be the right one for a particular application.

What is a 3-Part Syringe?

Before we get into the critical differences between these two types of syringes, we need to talk about the most widely used disposable syringe on the market—the 3-part syringe. When someone requests a disposable syringe, they’re often asking for a 3-part syringe.

3-part syringes are extremely popular due to their low cost, smooth gliding motion, and multiple functionalities they offer. The construction consists of a rubber gasket that sits on the tip of the plunger located inside the barrel.

As the plunger is drawn downwards or upwards, the rubber gasket acts as a sealant and creates a vacuum. One small caveat about this is that rubber tends to be a bit sticky when rubbed against a solid surface, such as the plastic barrel of a syringe. Because of this, a 3-part syringe uses a lubricant, like silicon oil, to prevent sticking and allow for a smooth downwards and upwards motion. For many applications, the lubricant oil does not interfere with the desired results, and the syringes work as intended.

However, for some medical, laboratory, and production applications, the lubricant can sometimes act as a contaminate and produce problematic results.

This is where a 2-part syringe comes in handy.

What is a 2-Part Syringe?

Commonly known by the brand name Norm-Ject® syringe, a 2-Part or "all plastic" syringe does not utilize a rubber tip on the plunger to create the vacuum seal. Instead, it uses a precisely engineered and slightly oversized plunger head that expands the barrel and creates a vacuum as it’s drawn downwards.

2-part syringes are made out of a polypropylene barrel and a polyethylene plunger and do not require a lubricant to work. They’re ideal for applications that cannot have the potential for foreign substances (such as silicon oil) to potentially interfere with the desired results.

Types of 2-Part and 3-Part Syringes

There are many different types of 2 and 3-part syringes on the market:

  • Luer Slip
  • Luer Lock
  • Eccentric
  • Centric
  • Catheter Tip
  • Oral Tip

These options generally all come in sterile and unsterile as well as by the box, case, in bulk, and mini-bulk.

Syringe manufacturers can also provide customized solutions for higher volume applications, such as:

  • Light-Restricting
  • Addition of Company Logos
  • Unique Colors
  • Special Volumetric Markings
  • Unassembled
  • Ungraduated

Frequently Asked Syringe Questions

Now that you know the difference between the types of syringes, we’ll share some of the common questions we hear about these syringes and answer them for you.

What are Syringes Made Out Of?

Syringes come in a wide variety of materials, such as COP, COC, Zylar, Borosilicate glass, Polyethylene, Polypropylene, and metal.

Can Syringe Selection Affect the End Product or Results?

Yes! If you’re a researcher or engineer and are having difficulties identifying the source of contaminants in your application, the lubricant that’s used in your 3-part syringe might be at fault.

Products such as the 2-part Luer Lock syringe from Air-Tite are manufactured from laboratory-grade polypropylene/polyethylene and do not contain styrene, DEHP, silicon oil, or rubber. They are latex-free and are ideal for applications that require a non-reactive, inert syringe.

What is the Difference Between Luer Lock and Luer Slip?

The key difference between Luer Lock and Luer Slip is that the Luer Lock syringe allows for twisting a needle onto the tip, which then becomes locked in place. On the other hand, Luer Slip allows for manual pushing of the needle into the tip. We have an article explaining these differences in more detail here.

What’s the Difference Between Eccentric and Centric Syringes?

You might hear the terms Eccentric and Centric (or Concentric) used when referring to a syringe. The main difference is that an Eccentric syringe tip is offset from the center and resides more towards the edge, whereas a Centric syringe tip is located in the center.

Centric and Eccentric refers to the location of the tip in relation to the body of the syringe. A Centric syringe has the tip located centrally. An Eccentric syringe tip is offset towards the edge of the body.

What Are Your Available Sizes for 2-Part and 3-Part Syringes?

Air-Tite carries many different sizes of 2-part and 3-part syringes from various manufacturers including:

  • 1ml
  • 3ml
  • 5ml
  • 10ml
  • 20ml
  • 30ml
  • 50ml

2-Part and 3-Part Syringes from Air-Tite

Air-Tite is an authority on syringes for the lab and industrial markets. Our very own Will Foley recently wrote an article for Drug Delivery Business News that discusses the difference between two-part and three-part syringes in more detail.

Read the Magazine Article

You can also see our wide selection of syringes by clicking the box below.