Cartridge : Federal 90gr Personal Defense Hydrashok Firearm : Kel-Tec P3AT with 2.75" barrel length Block calibration : All depths corrected (From 9.4cm @ 594 ft/sec) The front of the block was covered in 1 layer of 100% cotton, new and unwashed, fruit-of-the-loom T-shirt material. This material was chosen after reviewing several 100s of mugshot photos of violent criminals and their choice of upper body clothing. It also is representative of clothing worn most of the time in the southern US, where I lived at the time of the test. Average penetration was 12.0" Average expansion was 0.476" Average impact velocity was 839fps.