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What is SAPI and ESAPI Body Armor?

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There's a lot of jargon and acronyms used in the realm of body armor, which can be confusing for people who are new to the topic. In particular, we're frequently asked about the difference between SAPI, ESAPI, shooters cut and swimmers cut body armor. While these body armor types share common ballistic qualities, there are a few key differences including shape and size. When you're looking to buy body armor, it's important to know exactly what you're getting. In this article we're going to explore the key difference between the aforementioned body armor plates and provide a little background on each.


SAPI = Small Arms Protective Insert


As shown above, SAPI stands for Small Arms Protective Insert. It's important to note that the SAPI plates got their start in the U.S. Military as a means of classifying body armor designed to fit standard issue plate carriers. Military issued SAPI body armor plates are made from composite of ceramic materials (namely silicon carbide) and were designed to stop 7.62 x 51 (M80 BALL) rounds. In terms of NIJ threat protection level, SAPI body armor would be classified as level III under the current 0101.06 standards. If you're unfamiliar with NIJ threat protection levels, you can learn more about the subject in this article.


ESAPI = Enhanced Small Arms Protective Insert


In 2005 the U.S. Military began phasing out SAPI body armor in favor of the ESAPI plate, or "Enhanced Small Arms Protective Insert". This newer generation of body armor was designed in accordance with NIJ level IV specifications rated to stop .30-06 M2AP (AP stands for Armor Piercing) rounds. In comparison to SAPI plates, ESAPI plates are identical in size and shape. However, it's worth noting that ESAPI plates are also about 27% heavier than SAPI plates. ESAPI plates are typically made of a high-grade boron carbide ceramic which is even used for some armored vehicles such as tanks.


Shape: SAPI/ESAPI vs Shooters Cut vs Swimmers Cut


The image below illustrates the difference between the standard SAPI/ESAPI body armor plate shape and the more advanced plate shapes that Spartan Armor Systems™ has to offer. As you can see, the traditional SAPI plate design is a very featureless plate design. While this no-frills approach gets the job done, those who have worn SAPI plates can attest to certain limitations synonymous with SAPI plates. For example, SAPI plates tend to have more material in the shoulder area which can make the shouldering of a rifle feel awkward or unnatural. Conversely, shooters cut body armor has slightly less material in the shoulder area allowing for better range of motion and a more natural feel when shouldering a rifle. On the complete opposite end of the spectrum is the swimmers cut design which allows full range of motion in the shoulders. Another improvement worth noting is the shape of the bottom corners of our Spartan AR550 body armor plate. While the SAPI design may feel just fine while standing, the bottom corners become very uncomfortable when sitting or crouching. The Spartan AR550 Shooters Cut design was created to prevent much of the "digging" effect by removing the sharp bottom corners of the plate. To further improve the comfort and ergonomics of our body armor, Spartan Armor Systems™ offers a proprietary Advanced Triple Curve™ (ATC) design which is available for our Spartan Omega™ AR500 and Spartan AR550 steel core body armor products.




Plate Size Comparison

While commercial body armor plates are manufactured in standard sizes such as 8"x10", 10"x12" and 11"x14", the original SAPI plate sizes followed a different sizing method to fit the specific standard issues plate carriers they were designed for. While SAPI plates can be tailored more to the size of the wearer, producing so many sizes can be a challenge commercially. Another important consideration is that the size of most vital organs are roughly the same size for most people, only very short and very tall individuals need plates that differ from the common 10" x 12" size. In fact, it's a very common occurrence that customers who initially feel that they need 8" x 10" or 11" x 14" plates, discover that 10" x 12" plates are a much better fit for them. While this isn't the case 100% of the time, it happens more often than not. Lastly, it's important to note that commercially made SAPI/ESAPI medium sized plates are typically made in a 10" x 12" size despite their military counterparts being 9.5" x 12.5". Plate carriers made by Spartan Armor Systems™ can accept military issued SAPI plates despite the added .5" of height.

SAPI/ESAPI Plate Sizes

Commercial Plate Sizes

  • Extra Small: 7.25" x 11.5"
  • Small: 8.75" x 11.75"
  • Medium: 9.5" x 12.5"
  • Large: 10.125" x 13.25"
  • Extra Large: 11" x 14"
  • Small: 8" x 10"
  • Medium: 10" x 12"
  • Large: 11" x 14"



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To sum things up, SAPI and ESAPI body armor plates are a classification of armor used to identify a particular size, shape and threat protection profile of military issued body armor. While the SAPI plate design shares much in common with today's commercially available shooters cut design, there are some specific advantages to a shooters cut design when it comes to comfort and range of motion in the shoulders. Do you have questions about our body armor or tactical gear? We're always happy to answer your questions and help you choose the safety gear that's right for you. Please don't hesitate to reach out to us!


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