That item has a few faults which may decrease the fun with the new toy.
Aluminum may not be the best material for a fire piston as it is a fairly good heat conductor. In the picture the O ring protrudes too much from the piston. That will contribute to fast wear and indicates a bad fit of the piston. The surfaces of piston and tube show marks of improper cutting. If the inside of the tube is machined equally bad, the seal may be insufficient and further the wear of the O ring.
I would not buy it.