It has indexing on the ring. It's not small about 10 inches long. It does have an arm that goes against the mill to stop rotating.
Takes m3 to m12 taps
Perhaps if you posted the manuf and model of the item so folks could look up how it works. If it's a decent Tapmatic clone $65 shipped is a decent price. M3 to M12 is about 1/8" to 1/2" tap which is a tad larger than normally used in knifemaking. 2-56 threads are common.