Find it here: https://www.sparkfun.com/products/15583

Teensy 4.0 is the latest Teensy, offering the fastest microcontroller and powerful peripherals in the Teensy 1.4 by 0.7 inch form factor. It features an ARM CortexM7 processor at 600 MHz, with a NXP iMXRT1062 chip, the fastest microcontroller available today. Teensy 4.0 is the same size and shape as Teensy 3.2, and retains compatibility with most of the pin functions on Teensy 3.2.