Several strong and reliable bike lock brands are known for producing high-quality locks that offer excellent security against theft. Here are some top picks:

1. Kryptonite: Kryptonite is one of the most well-known and respected brands in the bike lock industry. They offer a wide range of U-locks, chain locks, and cable locks with varying levels of security. Look for their “New York” series for maximum protection.
2. Abus: Abus is a German brand that specializes in security solutions, including bike locks. They are known for their innovative designs and high-quality materials. The “Granit” series from Abus is highly regarded for its strength.
3. OnGuard: OnGuard offers a variety of locks designed for different security needs. They are known for their robust U-locks and chain locks. Their “Bulldog” and “Beast” series are popular choices for urban cyclists.
4. Hiplok: Hiplok is known for its wearable chain locks that offer both security and convenience. Their locks can be worn around your waist or carried like a traditional lock.
5. TiGr: TiGr specializes in lightweight and easy-to-carry locks made from titanium. Their unique bow-shaped locks are known for their strength-to-weight ratio.
6. Trelock: Trelock is a German brand that produces a range of locks, including U-locks, folding locks, and chain locks. Their locks often come with features such as anti-pick mechanisms and corrosion resistance.
7. Foldylock: Foldylock offers compact and folding locks that are easy to transport while still providing decent security. They’re a good option for those who value portability.
8. Master Lock: Master Lock is a well-known brand that also offers bike locks. While they might not have the same level of security as some specialized bike lock brands, they do offer affordable options for lower-risk areas.
9. Onguard: Onguard produces a variety of locks that cater to different security needs. They offer a mix of U-locks, chain locks, and cable locks at various price points.
10. Sigtuna Gear: Sigtuna Gear is known for its heavy-duty U-locks and chain locks that offer good security for the price. They are suitable for urban environments and moderate risk areas.

When choosing a lock brand, consider your specific security requirements, budget, and preferences. Always opt for locks with high-security ratings and features such as hardened steel construction, anti-pick mechanisms, and anti-drill protection. It’s also a good idea to read reviews and seek recommendations from other cyclists to ensure you’re making an informed decision.