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Fan Sizes & Bearing Types | Q&A

What fan sizes and thicknesses are most common?

  • Sizes: 80, 92, 120, 140, 180, 200 mm (120/140 mm are the mainstream).

  • Standard thickness: 25 mm.

  • Variants: 15–17 mm slim (space-constrained builds) and 30–38 mm thick (higher pressure, better against obstructions—space permitting).

Does a bigger fan always cool better?

  • At the same RPM, larger fans usually move more air and can be quieter for a given airflow target.

  • Real results still depend on case openings, filters, grills, and RPM control. Ensure your case supports the size you pick.

Which fan size is best for each use?

Size (mm) Typical thickness Typical use cases
80 25 Very small cases; spot cooling for add-in cards/boards
92 25 Narrow cases, legacy HDD bays, older cases
120 25 Most common for front/rear case fans and many CPU coolers
140 25 / 38 High-airflow or low-noise goals; case fans or radiators (when supported)
180 / 200 25 Large cases; high airflow at low RPM / silence-focused intakes

When should I use slim (15–17 mm) or thick (30–38 mm) fans?

  • Slim (15–17 mm): for tight clearances—ITX/SFF, shallow top/bottom mounts, interference near GPUs/PSUs. Expect somewhat lower airflow/pressure.

  • Thick (30–38 mm): where space allows and you need extra static pressure (radiators, dense grills/filters).

How do bearing types compare?

Bearing Typical lifespan* Characteristics & best use
Sleeve (oil-sleeve) ~5,000–15,000 h Lowest cost, very quiet when new; wears faster (oil migration), noise rises over time. Budget builds, light duty.
Hydro / FDB (fluid-dynamic) ~40,000 h Lubricated fluid dynamics improve durability and stability; quiet + long-running. Common in mid/high-end case/radiator fans.
Ball (dual-ball) ~50,000–100,000 h Very durable and heat-tolerant; tends to be noisier. Good for high-temp or 24/7 operation. (Single-ball hybrids ~40,000 h.)
MagLev (magnetic-levitation) ~50,000 h+ Rotor is magnetically suspended (minimal friction): very quiet, thermally robust, long life; typically higher price.

*Manufacturer ratings vary by model and operating conditions.

Which bearing should I choose?

  • Max longevity / tougher environments: Dual-ball or MagLev.

  • Best all-round balance (silence + life): Hydro/FDB (the mainstream sweet spot).

  • Lowest upfront cost / short duty: Sleeve (accept faster wear).

Any quick selection tips?

  • Pair size to case support and noise goals (140 mm if possible; 120 mm for universal fit).

  • Use slim fans only where clearance demands; use thick fans when you need extra pressure.

  • Match bearing to duty cycle and noise target (FDB/MagLev for quiet 24/7 use).

  • Always check filters/grills—they dictate whether you need pressure-oriented models.