Ampac is only available from them, they have the sole rights to their specific strain... it was discovered by one of their research scientist who is a professor at University of Alaska (may have the college name wrong, but its in alaska... going by memory) and patented by ampac...so you buy direct from the mfg when you order from them, super fresh in other words... plus it is a tough as nails species, very antagonistic toward the phytopathogens... good stuff (2 yr advertised shelf life)
there are a lot of products on the market now due to the increse demand from your indoor pot growing crowd, most will have some combo of the T22 strain and maybe one or two others with some Bacillus (sp?) bacteria added..
what you have to watch out for is how old is it, how was it stored, what is the spore count etc etc etc, most of your lil fly by night hydro shops dont refrigerate, or they remove the expiration dates... etc, best to deal with the major vendors, and even with them I have never got any that wasnt out of date on the first try... so I try to deal direct with the mfg... which isnt a prob usually,
back to work... break time over