2-position arch / level feature increases tripod's minimum / maximum height range and narrows 'footprint.' Unitizes leg sections to minimize flex during high-fluid drag panning. INCLUDED AT NO EXTRA COST with all 100mm single-stage & 2-stage tripods and 75mm heavy-duty tripods. This line item intended as replacement in case of loss or non-warranteed damage to CONTENDER unit included with tripod, or as an upgrade from discontinued MLS-100.