NTN is the OEM supplier of this part for Mitsubishi. So whether you purchase this tensioner in the original NTN box or repackaged as an Aisin (BTM-500) or Mitsubishi item (1145A070) - you're getting the exact same part; it even has NTN molded into the tensioner.
Monteros have timing belt driven interference engines that require a timing belt service every 60,000 miles. The 2nd most common reason that we see Monteros end up in junkyards (#1 being collision damage) is a blown engine resulting from a timing failure. Furthermore, we have seen countless Montero engines ruined from cheap aftermarket timing belt kits, usually because the tensioner, not the belt, failed shortly after install.
This high quality OEM, Made In Japan, Tensioner (AKA Adjuster) is probably the most important item on the entire vehicle that needs to be OEM. Although, no matter how high-quality your hydraulic tensioner is, the tensioner pulley needs to be preloaded with a special tool or else the tension will not be correct and this hydraulic tensioner will fail prematurely. Tensioner Pulley Preload Tool VT-LO-MD998767