The telescopic mid-level spreader allows you to set the proper leg angle and resulting tripod footprint. 537SPRB middle spreader is now re-engineered and more robust, toguarantee a flexible link between spreader and tripod leg.Variable middle spreader for quick and easy leg angle adjustmentMade in aluminumFlexible Link Between Spreader & LegsCompatible with the following Manfrotto tripods:350SPRB537SPRB545B546B546GB