Products Builder › Locknut for Old Arm Image 1 of 1 Locknut for Old Arm $5.00 (QO-LOCKNUT) Add To Cart Added! (QO-LOCKNUT) Replacement Locknut for older Flexible Mounting Arms. If you lose the part, this listing provides an inexpensive replacement option rather than purchasing a new Mounting Arm. Reviews Reviewer Name Review Date Star Rating Description Posted on Etsy Product Show More You Might Also Like Old Flexible Mounting Arm 24" $72.50 Clamp Screw $5.00