AFAIK ECHO1's is an A&K rebrand and the A&K is a clone of the Classic Army, which is itself derived from the old TOP one (along with the aftermarket gearbox that was made for it).
The other alternatives would be G&P and the ARES/STAR version (the ARES/STAR one is all plastic and thus much lighter).
I have an A&K one and it does the job. Almost identical to the CA, about 1 lbs lighter. Excellent bang for the buck. CA one might be a tad more robust.
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