Question 1

The listing mentions 12.9 & 10.9 Grade—why are the screws mixed, and which ones are which?**

Accepted Answer

Great catch! The 2,300-piece assortment combines two high-strength categories. Most of the M3 screws (the majority of the kit) are the premium 12.9-grade alloy, which is ideal for high-stress applications like 3D printer frames or RC motor mounts. However, some of the longer lengths (typically 30mm and 35mm) are 10.9-grade. You can differentiate them by the markings on the head—though with the black zinc coating, it can be tricky. If you are doing heavy structural work, check the specific length’s spec sheet. For standard assembly, electronics, and DIY, both grades are more than sufficient and will outlast the hardware you are replacing. TikTok reviewers specifically noted that mixing them is fine for general use, but they appreciated having the 12.9s saved for critical parts.

Question 2

Will these screws fit my Ender 3 or other common 3D printers?**

Accepted Answer

Yes, absolutely. This is arguably the most common use case in our reviews. M3 screws are the standard size for most 3D printer assemblies (frames, extruders, and hotends), fans, and enclosures. The kit covers the common lengths—4mm, 6mm, 8mm, 12mm, 16mm, and 20mm—which will handle the majority of stock and modded machines. However, note the lengths listed (M3x4/6/8/12 etc.) refer to the shaft length *underneath* the screw head. So, a M3x12 is a 12mm shaft. If you are upgrading to a specific custom part, double-check your print's recessed depth and thread engagement. If you are just building a standard kit, you are covered.

Question 3

The container seems big—is it durable for a workshop, and how is it organized?**

Accepted Answer

The container is a rigid, clear plastic case with individual segmented compartments. It is sturdier than a zip-lock bag but treat it as a *storage box*, not a "throwing in the bottom of a backpack" case. The biggest complaint from Reddit users isn't the hinge, but the lack of a printed size label on the top or dividers. We recommend spending 10 minutes with a permanent marker to label the segments. The case itself closes securely, but we advise against tossing it around loose in a toolbag; the case holds its shape, but the dividers are fixed, so there is no spill risk, just potential for scratched corners.

Question 4

Is the black zinc coating just cosmetic, or does it prevent rust?**

Accepted Answer

The black zinc plating serves two purposes: mild corrosion resistance and low glare. It is not a marine-grade coating. For indoor use, electronics, and dry environments, it offers substantial rust protection and looks great. We have no reports of surface rust from indoor users. However, if you are using these on an outdoor project (like a bike rack or exposed brackets) or in a high-humidity shop, they will eventually develop surface wear. The hex socket drive is machined after coating, which means the inside of the socket is bare alloy steel—be sure to dry your drivers or wipe them with a light oil if you live near the coast or in a damp climate to prevent the hex bit from rusting.

Question 5

The review says there are nuts and washers—are the nuts Nylock (nylon insert) or standard, and are the washers flat or split?**

Accepted Answer

The kit contains standard-threaded hex nuts (not Nylock) and flat washers. The nuts are free-spinning until they meet the bolt seating, which is perfect for quick assembly and stacking multiple pieces. If you are mounting something subject to high vibration (like a motor gantry or a CNC spindle), we recommend picking up a low-cost pack of Nylock M3 nuts separately to use in conjunction with this kit. The washers included are flat, general-purpose washers, ideal for distributing load and preventing scratching of surfaces. You won't find split lock washers in this set, so for vibration resistance, you will want to rely on thread-locker compound or you can source your own lock washers.

2300PCS M3 Screws with Nuts Assortment Kit, M3x4/6/8/12/16/20/25/30/35 mm Hex Socket Button & Cap Head Bolts Nut and Washers Set, 12.9 & 10.9 Grade Black Zinc Plated for DIY, 3D Printer

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