7mm hard drive bay
Most drives are currently 9.5mm high. Some new Thinkpads come with 7mm drive bays.
There are many discussions around the internet regarding this, here is a short summary:
- Hitatch Travelstar series that begin with model code "Z". This includes Z7K320, Z5K500, and Z5K320
- Momentus Thin Hard Drives | Seagate
- Micron/Crucial C400 series with "AK" in the model number (see below)
- note that Micron is Crucial's parent company. Micron manufacturers the "C" series while Crucial manufactures the "M" series. Reportedly, only the C series is compatible with the x220.
Modifiable 9.5mm SSD
- Micron/Crucial C300 with the spacer mod. See X220 SSD 7mm Mod (Crucial C300)
- Micron/Crucial C400/M4 with spacer mod. (still waiting on confirmation)
- Not all C400 models require a mod. "AK" = 7mm and "AC" = 9mm. Ex) MTFDDAK256MAM-1K1 = 7mm, and MTFDDAC256MAM-1K1 = 9mm. C4 Product Brief
- Intel X-25M with the spacer mod
- Intel 320 series with the spacer mod
- Kingston/Intel X25-E
- Intel 310 series
- MyDigialSSD (waiting confirmation, relatively unknown brand)
- Renice X3 (SF1222) mSATA SSD User Review
- OCZ Nocti
- Intel 510 SSD series
- Vertex 2 and 3 SSD series
Some people have also sanded off the protruding parts of the case which stop you inserting a 9.5mm drive without the caddy.
The moddable drives listed above tend to have a spacer which can be removed with ease and a top which can be replaced using shorter (M2) screws. Drives without the removable spacer can always be removed entirely from their shell and bodged in place.