[Worn] Iron Heart Thermals IHTL-1301 - Sizing and Shrinkage, Two Year Review

Iron Heart Waffle Knit Thermals IHTL-1301

Iron Heart’s midweight Waffle Knit Thermals have become a staple for us in our Fall/Winter wardrobe. Whether you live in milder climates like California or deal with some of the harsher winters in the Northeast, these thermals are versatile enough to wear no matter your location. Iron Heart does make a beefed up extra heavy version (IHTL-1700) for those who need it, but these midweight ones are solid all-around thermals that come in a variety of colors – Grey, Black, White, Olive, Navy, and Indigo (dyed). Sizing thermals can always be a little tricky, but we’re here to clear that up for you. Read on below for information on sizing, washing, shrinkage, and more.

Like all of Iron Heart’s products, these IHTL-1301 Waffle Knit Long Sleeve Thermals are made in Japan and constructed using the same heavy duty construction that they are known for. Using a 100% cotton waffle thermal knit, these are constructed using a 4-needle flat seam, which creates a minimalist seam that doesn’t add any thickness to the overall fabric. These originally came to market in 2013 starting with the Black, Grey, and White colors, and have since expanded in 2021 to include Navy and Olive variants in 2021.

These are generally stocked once or twice a year, but more recently in 2021-2022 have been more of a once per year kind of deal. Accordingly, if you’ve been waiting for some of these Iron Heart thermals to restock, we wouldn’t necessarily wait until the temperatures drop off a cliff. Plus, these are awesome come Thanksgiving-time, as you’ll appreciate the stretchiness and comfort of this fabric while you’re gobbling down multiple turkey legs.

Iron Heart Thermals IHTL-1301 in Navy, Black, Olive, and White Iron Heart Thermals IHTL-1301 in Navy, Black, Olive, and White Iron Heart Thermals IHTL-1301 in Navy, Black, Olive, and White


Our preference with wearing these Iron Heart thermals are basically to treat them like a base layer or t-shirt, except for the cooler months. Just as you would wear a white, black, grey t-shirt as your only layer or primary layer during Spring/Summer, and perhaps throw on a button-up shirt overtop, we like doing the same for Fall/Winter. Wear them on its own, or throw on the waffle knit thermal underneath a flannel to add some additional warmth to your nights beside the campfire.

In terms of color and their versatility, we’d put Grey as the most versatile, followed by White and Black as a tie or close-second, and finally Navy and Olive if you’re looking for more of a standalone thermal to wear. Grey works well as the most versatile color as it’s a pretty neutral color that doesn’t have the stronger contrasts that a black or white base layer might give when layered underneath another shirt.

Recently I’ve been wearing the Iron Heart IHSH-328-GRN 7oz Back Satin Military CPO Shirt – Green as an overshirt for the Fall season. A perfect combination of layers before things get too cold. The Iron Heart thermal provides a good amount of warmth, and the CPO shirt adds some wind resistance and color to the overall palette.

The Navy and Olive colors are obviously a bit more unique and thus require some color coordination and considerations if you’re wearing another shirt over them. In general though, you’ll be hard pressed to not find an appropriate occasion to wear each and every color.


These Iron Heart thermals come in a fitted cut. That is, some room in the chest that tapers a little through the torso and waist, and comes back out at the hem. In general, you can pick between a couple sizes for these depending on how slim you want these to fit.

Assuming you want to wear the thermals as a base layer or primary layer, we’d recommend taking the size that has a chest measurement that matches closest to your actual body chest measurement. For example, if you have a 40” chest, we’d generally recommend going with either L or XL depending on if you want a slimmer or slightly more relaxed fit.

With a 40″ chest, given the loose knit and stretchiness of this fabric, wearing size L will be snug/tight at first, but as you wear it in should stretch out nicely. Keep in mind that upon wash (discussed more below) these will get temporarily tighter; but more importantly the length of the overall thermal will come in a bit. So if you have a longer torso or just in general a taller person, you may need to opt for the size up so that the thermal doesn’t end up too short.

While Iron Heart does pre-rinse these to eliminate most shrinkage, the nature of this fabric is that when it hits a wash, it’ll come in quite a bit, but ultimately stretch back out. As we just noted, the primary thing to watch for is the length of the body and sleeves, as these shrinkages can be more permanent. In contrast, the chest will shrink post-wash, but stretch back out (and more). You can find some numbers below for a size Large in Grey, from a couple years ago that we’ve put through the cycles. Of note, on the chest measurement post wash/wear, is that it tapers in quite a bit from just under the armpits. The chest is actually closer to 21” if you go down just one inch from the chest and armpit seam. The area just under the armpit is likely exaggerated in the stretch due to that area getting the most tension during wear (moving arms up and down, crossing arms, etc.).

IHT-1301-GRY (Large) (measurements in inches)ChestBottomShoulderSleeveLength
Brand New201917.525.7527
Post Wash (machine warm wash + machine dry)22.5221923.424
Several Wears (post wash)2322.51923.524.25
Net Change+3+3.5+1.5-2.25-2.75

Iron Heart IHTL-1301-GRY Side-by-side comparison Front
Iron Heart IHTL-1301-GRY Side-by-side comparison angle
Iron Heart IHTL-1301-GRY Side-by-side comparison Side
Iron Heart IHTL-1301-GRY Side-by-side comparison Back

Additionally, we wanted to see how the thermals would fare if we didn’t put them through the machine dry and kept to cold washes. From this recent run of thermals, we also grabbed a size Large in Olive and you can see how the different washes will result in different shrinkages (much less shrinkage in both width and length as you would expect with a cold wash / hang-dry).

IHT-1301-OLV (Large) (measurements in inches)ChestBottomShoulderSleeveLength
Brand New19.51918.525.526.5
Post Wash (machine cold wash + hang dry)201919.252627
Second Wash + Several Wears (post wash)212119.52526
Net Change+1.5+2+1-0.5-0.5

Iron Heart IHTL-1301-OLV Side-by-side comparison front
Iron Heart IHTL-1301-OLV Side-by-side comparison Angle
Iron Heart IHTL-1301-OLV Side-by-side comparison side
Iron Heart IHTL-1301-OLV Side-by-side comparison back

As you can see (excuse the wrinkly thermal!), no matter the type of washing you do, the fabric will stretch back out in the chest. The body and sleeve length may come out a little as you wear it in, but our experience is that it will come out net short compared to the original, out-of-package brand new status.


The fabric itself is quite soft and doesn’t feel heavy or thick at all. However, the waffle structure does allow this to hit above its weight. So don’t be deceived once you get it in your hands and it feels a little light. As well, because of the waffle knit, it does have a somewhat sponge-like feel to it, especially if you grab a handful of the thermal and give it a good sqeeze.

Compared to some other thermals we’ve seen over the years, the Iron Heart thermals’ waffle structure is a bit more loosely packed in, which contributes to that lighter feel. It also means it has a slightly more casual look to it, whereas a tighter packed waffle structure might look a little more uniform and in our opinion less casual.

The hem on the body and the sleeve cuffs are finished with a chain stitch run-off, which can be a nice little detail if you enjoy that. As well, though not part of the fabric itself, an Iron Heart patch is sewn onto the bottom-left, front corner of the thermal. Just something to note!


I’ve gone through two Fall/Winter seasons in the IHTL-1301-GRY Grey thermal, and they’ve been a consistent staple in my winter wardrobe. Specifically for my thermal, since it has shrunk quite a bit in length(used to be 27”, now 24.25”), I use it primarily as a base layer underneath a flannel or jacket as the length is a tad short for my liking. The chest has widened a little, but that doesn’t bother me at all, and you can’t really notice it given just how much give and stretchiness the overall thermal has. The sleeve coming in about 2 inches is also just fine as it now fits a little better without scrunching up.

After many washes and wears, the main difference between a new thermal and the worn pair is that the color has lightened a bit – I’m guessing primarily due to the laundry detergent and perhaps just washing in general. The fabric doesn’t show any wear besides that (no thinning, no unraveled threads, etc.).

Iron Heart IHTL-1301-GRY Flat-lay side-by-side old and newIron Heart IHTL-1301-GRY Flat-lay side-by-side old and newIron Heart IHTL-1301-GRY Flat-lay side-by-side old and new

If anything I could say the elbow has shown some wear, but you’d be hard pressed to really identify that other than perhaps it being stretched out a little more (see zoomed in photo of the elbow area below).

Iron Heart IHTL-1301-GRY thermal elbow wear

There is some indigo crocking on the interior side of the back due to the rubbing as I sit down with a pair of denim. You can see a couple photos below of this, primarily behind the Iron Heart sewn patch is (really had to zoom in to see the indigo).

Iron Heart IHTL-1301-GRY Waffle Knit Thermal - Indigo Wear Iron Heart IHTL-1301-GRY Waffle Knit Thermal - Indigo Wear

My main advice for these is to keep them on the cold wash and hang dry protocol. The machine dry really knocks the socks off the length. And if you’ve got a shorter torso and prefer the shorter length, then you’ve got a path to a better fitting thermal. Whenever I feel like I’ve worn it a few times where it’s stretched out and gotten a little loose, I’ll throw it in the wash to shrink it back in.

The Grey Iron Heart thermal continues to be my recommendation for a versatile thermal for single layer and as an underlayer. But, the other colors – especially the Navy and Olive are my picks for standalone pieces when you just want a single layer.

Iron Heart Waffle Knit Crew Neck Thermals are available on our website in Black, Grey, Navy, Olive, White, and Indigo (dyed). We also carry the henley version of these waffle knit thermals in Olive and Indigo (dyed).

Shop our full Iron Heart collection here.

You can also find our review of the Iron Heart Loopwheel Tees here.

Iron Heart IHTL-1301-OLV, IHTL-1301-NAV, IHTL-1301-WHT, IHTL-1301-GRYIron Heart IHTL-1301-OLV, IHTL-1301-NAV, IHTL-1301-WHT, IHTL-1301-GRY Iron Heart IHTL-1301-OLV, IHTL-1301-NAV, IHTL-1301-WHT, IHTL-1301-GRY