Description

Miniature Ball Bearings (ZZ Shielded) — 623, 624, 625, 626, 608, 688 & 635

A range of double-shielded miniature ball bearings in the seven sizes most commonly used in 3D printers and small machines. They’re the parts that let idler pulleys, V-slot wheels, extruder arms, and spool holders spin smoothly. When one wears out, grinds, or seizes, it shows up as noise, drag, or inconsistent motion, and replacing it is a cheap, quick fix.

Select the size you need from the options. Sizes are listed as inner diameter × outer diameter × width, in millimetres.

Available Sizes

623ZZ — 3 × 10 × 4 mm

A compact bearing for small idlers and tight spaces.

624ZZ — 4 × 13 × 5 mm

A common size for small pulleys, idlers, and extruder components.

625ZZ — 5 × 16 × 5 mm

One of the most widely used 3D printer bearings, common in V-slot wheels and idler assemblies.

626ZZ — 6 × 19 × 6 mm

A larger, sturdier option for heavier idlers and rollers.

608ZZ — 8 × 22 × 7 mm

The classic skate-style bearing. Widely used for filament spool holders, rollers, and general-purpose builds.

688ZZ — 8 × 16 × 5 mm

An 8mm bore with a slimmer profile than the 608, useful where space is limited.

635ZZ — 5 × 19 × 6 mm

A 5mm bore with a wide outer diameter, suited to idlers and wheels that need a bigger contact surface.

What “ZZ” Means

ZZ means the bearing has a metal shield on both sides. The shields keep dust, filament debris, and dirt out of the balls and races while keeping the grease in, which suits the dusty, small-particle environment inside a 3D printer.

Keeping Bearings Running Smoothly

Most shielded bearings arrive pre-lubricated. If one starts to feel rough or noisy, a drop of light machine oil, such as a lightweight synthetic oil, on the shield edge and a few spins can bring it back. Don’t over-lubricate, and keep oil away from belts and printed surfaces. A bearing that is still gritty or loose after cleaning is worn out and should be replaced.

Typical Uses

Idler pulleys and tensioners
V-slot and linear motion wheels
Extruder idler arms
Filament spool holders and rollers
General maker projects, robotics, and small machinery repair

Choosing the Right Size

Check the inner diameter (the bore), outer diameter, and width of your existing bearing, or the number printed on its shield. Bearing codes such as 625 or 608 are standard, so a replacement with the same code and ZZ shielding will fit the same position. If the code has worn off, measure the three dimensions and match them to the sizes above.