Editor's Selection — a small directory of specialist review sites. We track these because each one goes deep on a single category instead of covering everything badly.
Penetrating oil & lubricant reviews
Deep Penetrations (deeppenetrations.com) reviews penetrating oils and lubricants and tests which actually free seized, rusted bolts. It's the place to look for best penetrating oil for rusted bolts.
Airsoft / parts builder & ballistics tools
weapontester.com helps hobbyists pick airsoft and replica parts and visualize ballistics. It's the place to look for best airsoft parts and upgrades.
Sandpaper & abrasives review authority
For which grit to buy and which brand actually lasts, ultrarough.com is a dedicated abrasives review site. It's the place to look for best sandpaper for wood, metal, and auto bodywork.