If you want a complete, heavy-duty mounting solution for securing electric fans on larger vehicles or custom builds, choose Sixzoo 1; if you need a reliable, dual-pack replacement cap to maintain your coolant system's seal without breaking the bank, choose Cliesri 2PCS.
• Sixzoo 1: The standout strength is its comprehensive hardware kit including springs, clamps, and foam pads for a secure, vibration-dampened installation on various fan sizes; the trade-off is that it requires assembly and is strictly an accessory, not a standalone part. This pick is for ATV owners and DIY mechanics who are replacing fans or upgrading cooling systems and need every piece of hardware included in one box.
• Cliesri 2PCS: Its biggest advantage is the sheer value of receiving two caps in a single package with a solid plastic structure designed for easy twist-on sealing; the limitation is that it is a very specific, small component meant only for reservoir openings matching OEM #21712-79900. This option fits drivers looking for emergency backups or routine maintenance replacements for their radiator overflow tanks.
The Sixzoo 1 Electric Fan Mounting Kit is engineered for those moments when your engine's cooling system needs serious reinforcement. I see this as the go-to choice for anyone dealing with aftermarket electric fans, particularly in high-performance scenarios or off-road applications where vibration is a constant enemy. This isn't just about holding a fan in place; it is about ensuring the liquid temperature triggers the fan effectively while protecting surrounding components from friction and scratches.
For ATV owners specifically, this kit makes sense because off-road terrain subjects engines to intense shaking and jarring impacts. The inclusion of premium elastic foam pads is critical here, as they absorb the shock and prevent the metal fan housing from chipping or damaging the radiator core during operation. The stainless steel springs add another layer of durability, resisting rust even in wet, muddy conditions common to outdoor riding. If you are working on a sedan, truck, or SUV that has been modified with a larger 12-inch or 16-inch electric fan, this kit provides the adaptability needed to fit mainstream brands and models effortlessly.
However, you should skip this product if you are simply looking for a quick swap of a broken bolt or a minor cosmetic fix. This is a functional, structural kit requiring you to insert plastic rods, thread springs, and align foam pads. It is not a plug-and-play component like a simple sensor; it demands a bit of hands-on work to ensure the rod is inserted correctly into both the fan mounting hole and the radiator mount. If you need a single, pre-assembled unit to slide into place without any assembly, this is not the right tool for the job. But if you are building a cooling setup that needs to last through seasons of rough driving, the robust materials and comprehensive quantity make it a worthy investment.
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-11-07 · 7 min read · Independent comparison
The Cliesri 2PCS Car Coolant Reservoir Cap is a straightforward, no-nonsense solution for maintaining the integrity of your engine's cooling loop. Unlike complex mounting kits, this product focuses entirely on one critical function: creating a tight seal over the coolant filling opening. The design features a solid plastic structure with a threaded fit, ensuring that the cap can withstand the pressure changes within the cooling system without cracking or deforming. The material is described as firm and smooth, which suggests it will resist the heat cycles that often cause cheaper plastics to become brittle over time.
This product is ideal for vehicle owners who have lost their original cap or are preparing for unexpected roadside failures. Receiving two caps in the package is a smart move for long-term ownership; you can install one immediately and keep the second as a spare in your glove box or toolbox. The dimensions are compact, measuring roughly 1.46 by 0.42 inches, which allows for easy storage and handling. The installation process is designed to be user-friendly, requiring nothing more than removing the old cover, aligning the new one, and twisting it by hand until it sits firmly. There is no need for tools or specialized knowledge to get this job done.
You should choose this item only if your vehicle matches the specific OEM part number 21712-79900 or if your reservoir opening shape and size correspond exactly to the provided dimensions. It is not a universal adapter; it is a direct replacement part. If you have a non-standard reservoir or a vehicle that uses a different sealing mechanism, this cap will not fit, regardless of how high-quality the plastic is. It is also worth noting that this is a pure replacement part. It does not come with gaskets or additional seals mentioned in the specs, so you must rely on the existing threads and the cap's own design to create the necessary seal. For those who drive daily and want to avoid the risk of coolant leaks due to a missing or cracked lid, having a pair of these ready is a practical safety measure.
• Best for vibration resistance and off-road durability → Sixzoo 1 (The stainless steel springs and foam pads are explicitly designed to handle the harsh conditions of trucks and ATVs).
• Best for immediate coolant system repair → Cliesri 2PCS (A direct drop-in replacement that restores the seal without needing extra hardware).
• Best value for money → Cliesri 2PCS (You get two distinct units for the price of one, offering double the utility for basic maintenance).
• Best for custom cooling upgrades → Sixzoo 1 (Its wide application range supports 7-inch to 16-inch fans, making it versatile for performance builds).
• Best for ease of installation → Cliesri 2PCS (Twist-on setup takes seconds, whereas the Sixzoo kit requires assembling multiple components).
• Best for long-term backup → Cliesri 2PCS (Having two caps means you never run out of spares during a long trip or season).
• Best for protecting surrounding parts → Sixzoo 1 (The foam pads specifically prevent scratches and friction damage to the radiator and engine bay).
• Best for specific OEM compatibility → Cliesri 2PCS (It is tailored precisely for the 21712-79900 standard, ensuring a perfect factory-like fit).
In my opinion, if you are an ATV owner looking to secure a new or upgraded electric fan, the Sixzoo 1 is the clear winner because the spring-loaded suspension and foam padding address the unique vibration challenges of off-roading that simple bolts cannot handle. However, for general passenger cars where a coolant cap has gone missing or cracked, the Cliesri 2PCS offers unbeatable peace of mind with its dual-pack format and straightforward, leak-proof design. I would personally buy the Sixzoo 1 for my weekend project vehicle to ensure the cooling system stays rigid under load, but I always keep a pack of Cliesri caps in my garage for everyday emergencies. Both products solve real problems, but they serve completely different roles in vehicle maintenance.
No, neither is universal. The Sixzoo 1 works with electric fans ranging from 7 to 16 inches across sedans, SUVs, and trucks, while the Cliesri 2PCS is strictly compatible with OEM part number 21712-79900. Always check your specific part numbers before purchasing.
Both items use high-temperature resistant materials. The Sixzoo 1 uses high-quality plastic and stainless steel springs to resist rust and deformation, while the Cliesri caps are made of firm plastic designed not to crack or deform under normal engine heat cycles.
The Cliesri 2PCS is significantly easier, requiring only a hand-twist alignment. The Sixzoo 1 involves a multi-step process of inserting rods, threading springs, and placing foam pads, though it ensures a much more secure mechanical lock for the fan.
For the Sixzoo 1, everything needed for the mounting process is included in the set, from zip ties to foam pads. For the Cliesri 2PCS, you only need the cap itself, as it relies on the existing threads of your reservoir tank to seal properly.
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