The THROOM®  6" KNOCKDOWN™ Reactive Target and the Pivot Base that it mounts on can be purchased separately or together in a Starter Kit. KNOCKDOWN™ targets react to hits by falling over backwards. Once knocked down, it stays down until reset manually or by pulling a string (see video below). Mount targets on soft wood stands using the Pivot Base or use with our Alpha Bracket Stand (Sold Separately).THROOM® targets and Pivot Bases are made of SHOOT-THROO™, our self healing material. Bullets pass through the polymer target and the Pivot Base. Secure the Pivot Base to your softwood target stand with (4) wood screws (provided) or with (2) THROOM® Nuts & Bolts (Sold Separately). To mount a KNOCKDOWN™ target on its Pivot Base, you simply snap it into place.For a different experience with the KNOCKDOWN™ Series Targets, mount the KD upside down for auto-resetting, swinging action (see video below).Best calibers:Reacts with all centerfire and rimfire rounds.Smaller caliber rifle rounds like .223 or 5.56mm should be shot at 75+ yards for KNOCKDOWN™ reaction.Large caliber rifle rounds like .308 or 7.62mm can be shot at 30+ yards for KNOCKDOWN™ reaction.Manual Reset with string pull