Notes on these sizes
623
The 623 is a micro bearing for extruder gears, small idlers and RC or gimbal pivots. A pocket this small leaves no room for error - a few hundredths of a millimeter decide whether the fit is press or loose.
F623
The F623 adds a locating flange to the 623 - in printed or soft materials the flange gives a micro bearing a positive seat, where a bare press fit alone would be asking a lot of the material.
695
The 695 is the compact 5 mm-bore option - small pulleys, extruder idlers and light pivots where a 625 is too bulky. Same bore as the 625 in a visibly smaller ring, for tight idler stacks.
F695
The F695 is the flanged 695, a signature of compact idler stacks - the flange registers each bearing against the printed wall, so a pair sharing one bolt stays square to it.
GE5C
The GE5C is a 5 mm spherical plain bearing - a pivot, not a roller. It belongs in rod ends and linkages that must articulate through angular misalignment, and its housing is its own problem: the joint slides inside the outer ring, so a bore that distorts the ring binds the whole joint.
625
The 625 is a 3D-printer staple - belt idlers, tensioners and small V-wheels ride on it, and its 5 mm bore drops straight onto M5 hardware. If a printer BOM names one bearing, it is usually this one or its flanged twin.
F625
The F625 is the flanged 625 - the flange sets the seating depth in belt-idler and roller mounts, which removes one dimension the pocket could get wrong.
608
The 608 is the bearing you already own - it is the skate-wheel bearing, and it turns up again in spinner toys, filament-spool holders and gantry idlers. Cheap and everywhere, which makes it the default answer when a printed part needs a bearing.
F608
The F608 is the flanged 608: the flange seats against the housing face, so the bearing sits at a controlled depth instead of wherever the press stopped. That makes it the forgiving choice for printed idler and pulley mounts.
These are standard reference numbers. Every machine prints and cuts a little differently - set a hole to 5.00 mm and it might land at 4.95 mm. Calibrate your machine in the FitCheck app and the clearance and pocket diameters here shift to match it. It's free in your browser, and the phone apps also work offline.
Metric and imperial clearances follow published mechanical-engineering references · heat-set pockets per CNC Kitchen · bearing housing seats follow published fit tables. Reference only - verify before you cut.