The 1-out-of-5 stars review does not even begin to reflect the poor quality of these boot wood stretchers, which (as I found only upon receiving them) are made in China.

On their very first use out of the box, one of the stretchers broke.  This was not due to applying undue torque to the stretcher's screw.  On the contrary, since it was the first stretching of a planned little-by-little series to avoid damaging the boots, only a pressure to just put a minimal tension on the boot was applied.  This was enough to fully split a section of the wood above the left top-rear hole for the metal arms; this holds a threaded short tube through which advances the long screw that separates the wood halves.  The wood is noticeably soft; the articulated long-screw does not turn smoothly, if at all, when at angles close to 90 degrees.  Buyer beware.