Product marketers love a good framework.

And let’s be honest — we’ve seen a lot of them. Some are helpful, most aren’t, and a rare few stick with you for years because they just work.

Brian Balfour’s Four Fits model is one of those for me.

I’ve keep coming back to this framework in my own work as a PMM because it combats one of the biggest myths in go-to-market: product-market fit is not the end game.

Today, I’m going to break down one of my all-time favorite frameworks and show how you can use it as a PMM to drive growth.

Let’s get into it.

The Four Fits Model

Getting to product-market fit is important, but if you don’t figure out how to acquire customers profitably, retain them, and then scale sustainably, you’ll be stuck in what Brian calls the "tugboat" phase, where every inch of progress takes disproportionate effort.

His framework outlines the four types of fit you need for real, sustainable growth:

• Market-Product Fit: You’re solving a real problem for a real market.

• Product-Channel Fit: You’ve found a way to reliably acquire customers.

• Channel-Model Fit: Your revenue model works with your acquisition channels.

• Model-Market Fit: Your business model can scale within your market.

When these four fits align, you’ll hit what Brian calls the "smooth sailer" phase, where growth happens naturally.

Market-Product Fit

Most of us were trained to think about product-market fit, but Brian flips it: start with the market, then build the product.

The big question here is: Is there a market with a painful enough problem that they will actively seek a solution? This is why jobs-to-be-done research is so powerful. Before jumping into product development, you need to:

• Identify your ICP’s core struggles (not just what they say they want, but what’s actually painful).

• Understand their willingness to pay. Is this a problem they'd pay to solve, or just a mild inconvenience?

• Map out alternatives. Is the market already seeking a solution, or are they living with the pain?

If you’re in B2B, this fit often determines whether you’ll get budget or just be a "nice-to-have" product.

Product-Channel Fit

Great products don’t sell themselves. You can have the best solution in the world, but if it doesn’t match the way customers find, evaluate, and buy solutions, you’re in trouble.

This is where product-channel fit comes in — your product has to be designed for the channels that will bring in the right customers.

• If you’re going after self-serve, you’ll need an organic acquisition loop (SEO, virality, product-led growth).

• If your best customers need education before buying, content and outbound sales might be the key channels.

• If you’re selling to enterprise, the product needs a sales-assist motion (demos, pilots, multi-touch engagement).

The biggest mistake here? Trying to force a product into a channel that doesn't match the natural buying behaviour of the market.

Channel-Model Fit

Let’s say you’ve nailed product-channel fit. Perfect. Now comes the next challenge: Does the cost of acquiring customers (your CAC) make sense with your revenue model?

This is where Brian’s ARPU ↔ CAC spectrum comes in. You need to make sure the cost of acquiring a customer makes sense relative to the revenue they generate.

• Low ARPU → Low CAC channels (think virality, SEO, product-led growth).

• High ARPU → Higher CAC channels (think outbound sales, paid acquisition, partnerships).

But the real risk? The ARPU-CAC Danger Zone. This is where your ARPU is too low to justify expensive channels but too high for cheap, low-friction ones.

To fix this, you’ll either need to increase ARPU (better monetization, upsells) or reduce CAC (shift to cheaper channels). If you don’t, growth will feel like a grind, and your unit economics won’t work at scale.

Model-Market Fit

Which brings us to model-market fit. We need to confirm the market is big enough for your revenue model to scale. Brian gives us a simple formula to check:

ARPU × Total Customers in Market × % Market Capture = Revenue Potential

If that number doesn’t get you close to $100M+, you’re either selling too cheap for your market size, chasing too small of a market for your pricing model, or overestimating how much of the market you can actually win.

To hit $100M+ in revenue, you need one of these models:

• Elephants (Enterprise) – 1,000 customers paying $100K/year

• Moose (Mid-Market) – 10,000 customers paying $10K/year

• Rabbits (SMB) – 100,000 customers paying $1K/year

• Mice (Prosumer, B2C) – 1M customers paying $100/year

• Flies (Ad-based) – 10M users generating $10/year (often via ads)

If you miscalculate here, you might get stuck in a niche too small to sustain the business.

Applying the Four Fits

When these four fits click, growth gets easier.

Most startups and scale-ups that struggle with growth are missing one of these pieces. And the solution isn’t always just more marketing. Sometimes, it’s adjusting the model, the channels, or even the core market itself.

This is why I love Brian’s framework. It forces you to zoom out and look at the whole picture instead of obsessing over just one piece in isolation.

So next time you’re troubleshooting growth, ask yourself:

• Which of the Four Fits might be off?

• Where does your biggest friction come from?

• What would happen if you adjusted one of these levers?

CAMPER ESSENTIALS

📚 Reading List: Dig into Brian Balfour’s seven part series on the Four Fits to go deep on each component. He includes a ton of helpful charts and formulas.

⚒️ Tools: I recently stumbled across this great video and screen recording tool called Tella. It’s the best of of Loom and Descript squished together. I’ll be using it for my next video project.

Until next week,