MonsterBass Flatline Crankbait Review

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The MonsterBass Flatline is the latest flat-sided crankbait to enter into an already saturated market of other similar baits from different brands. But, I must say the Flatline didn’t fall right out of the same mold as many of these other baits. A loud rattle, slightly larger than normal body, the bill design, a quality set of hooks and some bold colors separate it a little from the pack in key areas. Let’s take a closer look at the Flatline Squarebill now.

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In the interest of full disclosure, I do a good bit of freelance writing for MonsterBass as well. But they’ve never once asked me to promote a bait of theirs that I didn’t believe in, nor have I done so. And, I’m not even promoting this bait, so much as giving notes on my experience with it and talking through some of its key features.

All that being said, the first time I tied this bait on, I went to catching fish. I was fishing on a fairly cold winter day back in early December after a heavy rain and decided to try out the Flatline, since MonsterBass had sent over a few for testing. This bait is new for 2024, unveiled to the public via MonsterBass’s December subscription box—though it can now be purchased individually at

The water temp was 51 degrees, so not brutally cold, but still only a couple clicks out of the 40s. The visibility was portably at around a foot. The Crawlisious looked like as good a color to try as any given the conditions, so I tied it on and began chucking it on rocky points and banks. I didn’t catch anything big on it that day, but I did boat 5 or 6 small spots fairly quickly, and feel confident that a big one would have certainly bit it had I crossed paths with one.


Armed with Mustad treble hooks (you can’t ask for a better set of hooks on a squarebill) MonsterBass did something a little different with this bait. Choosing to almost always put a red hook on the front of their baits, MonsterBass stayed true to form here again in hanging a red hook on the front of the Flatline. It has long been believed by many that any little flash of red in the water signifies to a predator that the prey is injured and bleeding. A few other companies do this as well, so it’s not unique to MonsterBass, but it’s a nice touch worth noting.


This is a squarebill crankbait, which actually helps it standout a little against many other flat-sided baits. Some of the greats in this genre have more rounded bills, like the SPRO Lil John 50. And while there are other flat-sided baits that have square bills as well, it was worth noting here again that this, slightly larger flat-sided crankbait has a thick, square bill, perfect for deflecting wildly off cover.

And, having crashed this bait into a good bit of rock and wood, I can attest to the fact that it corrects itself quickly upon restarting the retrieve—there’s no blowing out to one side or the other with this bait.


Flat-sided crankbaits are tailor-made for cold water conditions. The tight wobble of these baits appeals to lethargic bass, which are often disinterested in the more aggressive movements of wider wobbling baits. I like the larger profile of the Flatline as well, since I believe it helps the fish see it and sense it better in muddy water. And, where many of these crankbaits are silent or have faint rattles, the Flatline lets a bass know it’s in the area.


With a loud and hard rattle, the Flatline stands out from the majority of its competition and makes for a bait that’s easy to target for cold-blooded, slow moving bass. Bass don’t like to chase baits all that much in the winter; thus spinnerbaits, vibrating jigs and crankbaits with loud rattles work really well at alerting the fish to their presence in the water by way of vibration and/or sound. If you reel the Flatline by a bass, it’s sure to feel it coming and will likely take a swipe at it on the way by.


the MonsterBass Flatline Squarebill comes in at $8, a good price for a loud, flat-sided crankbait that stands out in both size and sound. The square bill helps this bait roll over cover well, and the Mustad treble hooks are deadly if and when a bass takes a swipe at the bait.

The MonsterBass Flatline weighs 5/8 ounce, which makes for easy casting. And it’s rated to dive 2- to 4- feet, but can certainly go a little deeper if you play with the line size and the orientation of your rod tip. With 8 color selections, the Flatline is a solid bait from a subscription box company that has become an emerging lure manufacturer in its own right over the last few years.