The best 5/16-inch lag bolt depends on the wood project, exposure to moisture, and how many fasteners you need. Fayeploo and EASTPUK are 10-piece stainless steel options supplied with washers; Party Animals offers 20 stainless steel screws; Prime-Line provides 25 zinc-plated steel screws; and Tandefio is best for buyers who need a 100-count galvanized set. Compare the listed dimensions, material, finish, and included washers before choosing.
| Product | Best For | Pack Details |
|---|---|---|
| Fayeploo 5/16 x 5 | Stainless steel with washers | 10 screws and washers |
| Tandefio 5/16 x 5 | Large projects and bulk quantity | 100 screws and washers |
| Party Animals Black 5/16 x 5 | Black finish and outdoor use | 20 screws |
| Party Animals Stainless 5/16 x 5 | Stainless steel in a 20-count pack | 20 screws |
| Prime-Line 5/16 x 5 | Zinc-plated steel and 25-count pack | 25 screws |
Fayeploo 5/16 x 5 Stainless Lag Screws
Best for buyers who want stainless steel lag screws and matching flat washers in a small pack. The set contains 10 screws and 10 washers. The screws are listed as 304 stainless steel, 5/16 inch in thread size, and 5 inches long, with partial threads and a 1/2-inch hex drive.
Fayeploo lists the lag screws as meeting ASME B18.2.1 Commercial/Industrial Grade A2-70 and the washers as meeting ASME B18.22.1. This makes the set a clearly specified choice for wood fastening where the included washers are useful. Choose it if a 10-set quantity fits the job. Its pack is relatively small for projects requiring many fasteners.
Tandefio 100-Pack Galvanized Lag Bolts
Best for larger construction or maintenance jobs that call for a high fastener count. Tandefio includes 100 lag screws and 100 washers. The listed size is about 5/16 inch in diameter and 5 inches long. The product description identifies a hot-dip galvanized coating and a double-layer coating process, intended to provide corrosion resistance.
Choose this set if bulk quantity and included washers matter. The product recommends using guide holes to make installation easier, so plan for that step. The listing describes the bolts as black and galvanized; check that the finish and appearance suit your project before ordering.
Party Animals Black 5/16 x 5 Lag Bolts
Best for buyers who want a black finish and a 20-piece pack for wood framing, deck joists, or similar projects. The listing describes these as 5/16-by-5-inch hex-head lag bolts with deep threads, a sharp point, and a Dacromet coating. It states that the coating is intended to resist corrosion in outdoor and wet environments.
The product description also identifies the screws as 304 stainless steel. Since the stated material and coating combination may be important to project selection, verify the product details if a particular base metal or finish is required. Choose this option when its black appearance and listed coating fit the job; avoid assuming it includes washers, which are not listed in the package details.
Party Animals 304 Stainless Steel Lag Bolts
Best for wood projects where a 20-piece pack of 304 stainless steel screws is the priority. These hex-head lag bolts measure 5/16 by 5 inches, according to the listing. The product description highlights deep threads for grip and identifies decks, joists, posts, and framing as intended uses. It also describes a sharp point and clean threads for installation.
Choose this product if you want the listed stainless steel material without a black finish. It is a screw-only pack based on the available package information, so buyers who need washers should confirm whether they are available separately. The listing does not specify a wrench size.
Prime-Line 5/16 x 5 Zinc-Plated Lag Screws
Best for buyers seeking a 25-count pack of zinc-plated steel lag screws. Prime-Line lists the fasteners as 5/16 inch by 5 inches, made from A307 Grade A zinc-plated steel. The screws have a six-sided hex head and deep wood-screw threads. The listing notes that they do not accept a nut, so they are intended to fasten into wood rather than serve as a bolt-and-nut connection.
Choose this option when its size, steel material, finish, and pack quantity fit your project. The listing does not include washers or describe the screws as stainless steel. For an application exposed to moisture, confirm that zinc-plated steel is suitable for the conditions.
Buying Guide: How to Choose a 5/16-Inch Lag Bolt
Does the length and diameter match the project?
These selected products are listed at 5/16 inch in diameter and 5 inches long. Check the required embedment and the total thickness of the materials being joined before buying. A screw’s stated length may be measured from a particular point on the head; Fayeploo specifies that its length is measured from under the head. Review the individual listing when exact dimensions matter.
Which material and finish should you choose?
Stainless steel is a relevant option when corrosion resistance is a priority; several listings identify 304 or 18-8 stainless steel. Galvanized and zinc-plated finishes are separate choices offered by the products in this guide. Do not treat coatings or material descriptions as interchangeable. Match the listed material and finish to the project environment, and verify details when exposure conditions are demanding.
Do you need washers or a large pack?
Fayeploo and EASTPUK list 10 screws with washers, while Tandefio lists 100 screws and 100 washers. The Party Animals and Prime-Line listings do not specify included washers. For a small repair, a 10-piece set may be sufficient; for repeat construction work, compare the bulk pack quantity with the number of fasteners required.
Should you drill a guide hole?
Tandefio specifically recommends guide holes to make installation easier. Follow the product instructions and project requirements for other screws, too. Check the head style and needed tool: the Fayeploo listing specifies a 1/2-inch hex drive, while the other product details do not provide a drive size.
Frequently Asked Questions
What does 5/16 x 5 mean on a lag bolt?
It identifies a nominal diameter of 5/16 inch and a length of 5 inches. Check the product listing for how length is measured.
Are lag screws the same as bolts that use a nut?
Lag screws have wood-screw threads and fasten into wood. Prime-Line specifically states that its lag screws do not accept a nut.
Which option includes washers?
Fayeploo and EASTPUK list 10 sets with washers, and Tandefio lists 100 screws with 100 washers. Check each product’s package details before purchasing.
Which product is best for buying in bulk?
Tandefio is the largest listed pack in this selection, with 100 lag screws and 100 washers.
Are all 5/16 x 5 lag bolts stainless steel?
No. The products include stainless steel, hot-dip galvanized, and zinc-plated descriptions. Confirm the material and finish for the specific product you select.