Sold Individually. These are custom-machined and anodized billet aluminum mounts, which are special order for your tube outside diameter (OD) size from 3/4" to 2". While we do carry some of the common sizes in stock, please expect up to 10 days for your mounts to ship. (3/4", 7/8", 1", 1-1/4", 1-1/2", 1-11/16", 1-3/4" & 2" sizes available) Please measure tubing using a dial caliper to get the correct size, and measure at least 6" from any bends. The clamps are tightened using 4 stainless steel clamping bolts. There is also a positive engagement set-screw for additional security and to prevent rotation. An extra long 6mm bolt is included for mounting your deck lamp (or other accessory). There is counter-sunk clearance built into the lamp side of the clamp to allow tightening of the lamp (with a socket wrench) to the clamp before mounting the clamp on the tubing.