On one side, there are traces leading to two rows of holes spaced 0.1" apart for a 44-QFP pinout, while on the other side, there's a 44-QFN. Solder your chip to either side, and you're ready to mount it on any solderless breadboard.
Each item comes with three PCBs, and each PCB is identical and can accommodate a 10 mm square, 0.8 mm spaced QFP or a 7 mm square, 0.5 mm spaced QFN chip. Standard thickness PCB with a 0.7" gap between the two rows.
You can order the SMT Breakout PCB for 44-QFN or 44-TQFP - 3 Pack from the Adafruit category at SAMM Market with competitive prices, same-day shipping, and fast delivery advantages.