uxcell 12pcs m4 x 20mm star knobs, plastic hex shaped clamping knob screw hand tightening replacement knob for umbrella base replacement knob is up for auction in Patio, Lawn & Garden. The current bid is $1.00, 86% below the $7.09 MSRP, in New/Like New condition. Bid on this item at our Rogers - N Dixieland Rd. location before the auction closes.