REVIEW – 2025 has seen bike thefts skyrocket in NY. Bikes and e-bikes are everywhere, and so are the thieves. Alarms and bike locks have become a mandatory accessory if you want ot hold on to your prized bikes. Some thieves carry cutting tools, so not just any lock will do. You need one that can stand up to cutters and grinders long enough to make the theft too risky. Enter the Seatylock Mason 300 Bike Lock.
︎ Jump to summary (pros/cons)
Price: $90
Where to buy: Seatylock website, Amazon
What is it?
The Seatylock Mason 300 bike lock is a high-security U-lock designed for robust bicycle protection, including e-bikes and scooters. It features a patented triangular hardened steel shackle profile, which is lighter and 30% stronger against twisting and bending attacks compared to traditional round shackles. This lock has a double deadbolt locking mechanism that secures the shackle on both sides, requiring a thief to cut through twice, enhancing security. The lock is lightweight yet sturdy, with an inside clearance of 300 mm by 115 mm, making it versatile for locking various bike frames and accessories.
What’s included?
- 1 x Seatylock Mason 300 Bike Lock
- 3 x Keys
Tech specs
- Inside dimensions: 300 mm x 115 mm
- External dimensions: 170 mm (width) x 36 mm (depth) x 365 mm (height)
- Weight: 1,720 grams
Design and features
- 20/20 DIAMOND SOLD SECURE ULOCK: Best Portable & Solid Professional Bike Lock to Protect Your Bicycle. Pro Equipment for City Outdoor & Urban Cycling. Bolt Cutter Drill & Saw Proof. Mounting bracket to hold the Lock is Not Part of This Product and is Sold Separately
- 3-YEAR PEACE OF MIND PATENT ULTRA STRENGTH HEAVY DUTY ANTI-THEFT TECHNOLOGY: Thick Anti-Cut Waterproof Weatherproof Protector with Antitheft Pentagonal Shaped Crossbars. Hardened Steel Components for High-Level Theft Prevention
- SUPER WIDE OPENING FOR EASY LOCKING: Opens to Extra Huge 115 MM – 4.52 INCH Size Clearance for Maximum Long Locking. Oversized for Flexible Free Range of Use & Fast Protection Anywhere. No Chain or Code Required!
- UNIQUE AUTOMATIC CYLINDER SHUTTER: Super Specialized Anti Rust Dust Dirt, Water & Weather Proof Gear for e-Bikes, Ebikes, Electric Bikes, Scooters & Motorcycles. Quality Anti-Rattle Silent Design
- DOUBLE PROTECTIVE DEADBOLTS FOR TWIST ATTACKS: Smart Strong Safety for Cycles. Tough Hard Anti-Theft Guard Device with Security Kit – Keys & Nylon 6 Silicone Cover Case for Safe Frame
The Seatylock Mason 300 Bike Lock features a patented pentagonal hardened steel crossbar profile, which the manufacturer has stated is stronger than traditional rounded crossbars. It has a double deadbolt locking mechanism. For a bike lock, it is relatively weighing approximately 3.8 pounds. It includes an automatic shutter mechanism that keeps dust, water, and dirt out of the lock cylinder. The metal is rust-resistant, and the plastic coating provides UV protection.
Performance
The Seatylock Mason 300 Bike Lock is well constructed and easy to open and close. It is sturdy and has a great locking mechanism with waterproofing. The lock features a U-shaped design that allows you to lock the bike wheel to the frame of the bike to an external anchor. I have cone standard/conventional bike that I custom built, and this lock can be used with the bike for most locking scenarios. However, that is where things stop for me. I have multiple e-bikes, and all have 20*4 or 20*5 tires. I also have an e-motorcycle and a gas motorcycle. The most this lock can do on my e-bikes is lock a few spokes to the frame. The photo above shows the lock on my Honda Rebel 500 SE, and as you can see, it cannot fit around the tires, so it only serves to lock the spokes to the frame or the frame to a nearby anchor. I make this point because many places I go, like trails and Preserves, do not offer any external anchoring opportunities; the only way to lock the bike is to itself to prevent someone from riding away. All of my e-bikes are quite heavy, so it is very unlikely that someone can run off with any of them when they are locked to themselves unless they have a vehicle to assist. This lock does work for me since I use it to lock 2 frames together. So, two heavy ebikes locked together are a challenge for anyone without help and a vehicle. I will use this lock when I go riding with my family. This lock, used along with another lock, will keep our bikes secure. I must mention that while I do think that a grinder can eventually cut through, the thief will need time and space to do so. This is a robust and secure lock that is perfect for some bike security applications. We just need more designs that compensate for fat tires.
Final thoughts
The Seatylock Mason 300 Bike Lock is a secure lock that works well for standard bikes and some e-bikes with slim tires. Many e-bikes now come with fat tires, and this lock only allows you to lock a few spokes to the frame or the frame to an external anchor if available.
What I like about the Seatylock Mason 300 Bike Lock
- It is well built
- It is easy to use
- It comes with 3 keys
- It provides good security
- It is easy to open and close
What needs to be improved?
- It could be wider to accommodate the fat tires of most e-bikes
Price: $90
Where to buy: Seatylock website, Amazon
Source: Seatylock provided a free sample for this review. Seatylock did not have a final say on the review and did not preview it before it was published.
