MLB: What Does Flex Base Jersey Mean? (And How It Fits)

If you are a baseball fan looking to add a jersey to your fan collection, one jersey type that you will come across while shopping is a ‘Flex Base’ jersey. And since jerseys can be a bit expensive, it’s best to understand what this is describing before you make the purchase. What does flex base jersey mean?

Flex Base is type of MLB jersey (produced by Majestic) which is made in a way that reduces overall jersey weight and enhances mobility. Flex base jerseys are what the players wear in Major League Baseball.

The most notable feature of Flex Base jerseys is the mesh paneling below the waist which increases air flow and mobility for a lighter, cooler, more comfortable fit for players. This is what an authentic MLB jersey looks like (affiliate link takes you to

But how does this apply to you buying a jersey? In this article we will discuss the sizing of these jerseys and what kind of fit you an expect. We will also discuss the other types of fan jerseys

*Nike Update*

Starting Jan 1st, 2020, Nike became the official outfitter of MLB. This is what the new Nike MLB jerseys look like (affiliate link takes you to

The new Nike jerseys will not use the term “Flex Base” like the old Majestic jerseys did.

A lot of the old Majestic jerseys are on clearance if you want to browse for deals. Click here to check out the clearance jerseys at (affiliate link takes you to Majestic was the previous outfitter of MLB, so you can get some great deals on the old jerseys.

  • To read about how the new Nike jerseys fit, visit our article: MLB Jersey Sizing Guide

What Are Flex Base Jerseys?

Flex base jerseys are the official on-field jersey of Major League Baseball. They are the jerseys that the pros wear.

In 2016, Major League Baseball transitioned away from the traditional double-knit style of jersey, which was heavier, and transitioned to the Majestic Flex Base jersey using (among other things) input from Major League Baseball players to help design the make and fit of the jersey.

Flex Base jerseys are engineered with lighter-weight twill technology which combines with the mesh paneling to create a jersey that promotes easy movement for players.

Baseball fans have essentially two main types of jerseys to choose from if they are looking to purchase a fan jersey: Authentic and Replica. The Authentic jerseys are true matches to what the players wear on the field – meaning that Authentic fan jerseys are made with the same Flex Base jersey style that the players’ jerseys are.

Authentic jerseys are the premium piece of baseball fan apparel, and because of that, can be quite expensive. Let’s look at some of the notable features that these jerseys offer.

Flex Base Authentic Jerseys

If you are in the market for a fan jersey, Flex Base Authentic jerseys will be one of your options.

1. If you open up that link to the jersey on MLB Shop, you will instantly see the mesh paneling on the back waist of the jersey. This is something that is available on the Authentic Flex Base jerseys, but not the Replica Cool Base jerseys. Although this is a great addition for the players because it adds mobility and retains less heat, for some fans they might not like how it looks. You will have to decide if that is the style you are looking for. If you are wanting an authentic on-field jersey, this is the only style you can buy Authentic jerseys in, so you will have to learn to like it.

2. The Flex Base Authentic jerseys will be very long because they are true matches for what the players wear, and the players need long jerseys so that they can be tucked in and stay tucked in. The Flex Base Authentic jerseys run 2.5 inches longer than the Cool Base Replica jerseys.

3. The Authentic jerseys will have premium finishes in comparison to Replica jerseys, like sewn on tackle-twill graphics. Despite these premium finishes, the jerseys are still machine-washable.

Flex Base Fit

The Flex Base Authentic jerseys will fit true to size throughout the chest, but will run very long – even longer than replica MLB jerseys. As we detailed in the section above, authentic jerseys run 2.5 inches longer than replica jerseys.

For complete size and fit, check out our MLB jerseys size and fit guide.

Future of MLB Jerseys

The landscape of MLB jerseys is set for another major change in 2020, when Nike takes over the exclusive rights for MLB. As fans, we can expect another major change in the style and fit of jerseys.

Although there is no clear idea yet of what major changes Nike may make regarding the fit of MLB jerseys, such details should start to emerge in the second half of the 2019 MLB season.

Paul Johnson

Paul has been with us from our beginnings. He focuses on a wide range of sports, including NFL, NBA, MLB and golf.

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