These are $1.75 per in my area.
The box says Suppressor Specific, 300 Blackout.
16 inch bolt chrono results;
Ave = 1111
Max = 1149
Min = 1052
9 round test.
12 inch semi auto chrono results
Ave = 1095
Max = 1114
Min = 1079
10 round test, cycles, lock open on last round.
Magnetospeed Chronograph.
I think these are geared toward 10 inch or less barrels, I observed loud reports for most of the tests.
It was about 58 F during the test.