If you have ever torn down an RC car, rebuilt a classic motorcycle carburetor, fixed a printer, or repaired a lawnmower, you have run into them. You might know them as E-clips, E-rings, side-mount circlips, or by their official engineering designation: DIN 6799.

But to anyone who has ever had one ping off a screwdriver and vanish into the deepest, darkest corner of a workshop, they are universally known as the “Jesus Clip”—because that is usually the first word out of your mouth when they take flight.

Despite their reputation for launching themselves into parallel universes, the E-type circlip is a brilliant piece of engineering. Here is everything you need to know about how they work, why they are used.

What Exactly is an E-Clip?

An E-type circlip is a semi-flexible retaining ring stamped from spring steel, stainless steel, or beryllium copper. It gets its name from its distinctive “E” shape.

Unlike standard internal or external circlips—which form a nearly complete circle and require special expandable pliers to install over the end of a shaft—the E-clip is a radially installed fastener. This means it pushes directly onto the side of a shaft into a pre-machined groove.

The three prongs on the inside of the “E” are the secret to its success. The two outer prongs grip the bottom of the shaft’s groove, while the raised center prong applies pressure to the top, locking the clip firmly in place and creating a strong shoulder to prevent gears, bearings, or linkages from sliding off.

Why Engineers Love Them (and Use Them Everywhere)

E-clips are incredibly popular in manufacturing for a few key reasons:

• No End-of-Shaft Access Needed: If a groove is located in the middle of a long, complex axle, sliding a standard snap ring all the way down from the tip is impractical. An E-clip can be popped on right where it is needed.
• Low Profile: They require very little clearance, making them perfect for tight spaces like consumer electronics, power tools, and automotive dashboards.
• Cost-Effective: They are cheap to manufacture, incredibly lightweight, and require a simpler groove design than many other retaining methods.

Choosing the Right Size

When ordering replacements, remember that Metric E-clip sizes are based on the shaft groove diameter, not the outer diameter of the clip itself. For example, a 5mm E-clip is designed to fit into a groove that has been machined down to exactly 5mm, even though the total width of the clip will be noticeably wider.