Thisbottle kitsenables you to turn almost any bottle into an electric lamp. These pre-wired kits come with 8'gold cord complete, off/on socket,rubber adaptor, steel nipple, check ring and knurl nut. The cap is a slightly darker color than the shell. The diameter of the adapter is3/4"- please make sure that's the size you need. We also have 15/16" and 1/2" sizes. Adapter squeezes into bottle hole, then your able to push nipple into the hole of the adapter. The size of the adapterin this kit is 3/4".We ship with other items to save shipping costs. $6.16 each. Shipping is $3.90 for one and $.72 for each additional kit.Combined shipping- to get cheapest shipping costs (when buying different items)please buy what you need and “request invoice” so we can send invoice with lower shipping costs."How to Request Invoice when using shopping cart"---From your eCRATER cart, near the top of the page, move your mouse curser over our name “lamppartsguy” and a drop down menu will appear with the option to request invoice from seller.