UA Base 4.0 is built for extreme cold weather and lower activity. It uses a unique pattern that's designed to trap heat without adding bulk. Think long underwear, revamped for today's top athletes.
Long Sleeve
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Polyester / Elastane Blend
Zip
Fitted / Next to Skin
Hiking
Skiing
Fitness & Training
Size Guide
| Size | Chest (in) | Waist (in) |
|---|---|---|
| XS | 31 - 34 | 28 - 29 |
| S | 34 - 37 | 29 - 31 |
| M | 37 - 41 | 31 - 34 |
| L | 41 - 44 | 34 - 37 |
| XL | 44 - 48 | 37 - 41 |
| XXL | 48 - 52 | 41 - 45.5 |
| 3XL | 52 - 56 | 45.5 - 50 |
| 4XL | 56 - 60 | 50 - 54.5 |
| 5XL | 60 - 64 | 54.5 - 59 |
Compression — Ultra-tight, second-skin fit that keeps you locked in.
Fitted — A slimmer, athletic cut that allows total mobility but eliminates the bulk of extra fabric.
Loose — Fuller cut for complete comfort, total range of motion and greater breathability.
Chest — Place tape measure under your arms at the fullest part of your chest, wrap around your body until your fingers meet and mark the measurement.
Waist — Measure around your natural waistline. Be careful not to squeeze too tight to allow give.
Tall Sizes — All tall sizes are 2" longer than regular sizes. Sleeve lengths are adjusted proportionately depending on silhouette.
| Size | US Size | Waist (in) | Hip (in) |
|---|---|---|---|
| XS | 28 | 28 - 29 | 33 - 34 |
| S | 30 | 29 - 31 | 34 - 36 |
| M | 32 - 33 | 31 - 34 | 36-39 |
| L | 34 - 36 | 34 - 37 | 39 - 42 |
| XL | 38 - 40 | 37 - 41 | 42 - 46 |
| XXL | 42 - 44 | 41 - 45.5 | 46 - 50 |
| 3XL | 46 - 48 | 45.5 - 50 | 50 - 54 |
| 4XL | 50 - 52 | 50 - 54.5 | 54 - 58 |
| 5XL | 54 - 56 | 54.5 - 59 | 58 - 62 |
Compression — Ultra-tight, second-skin fit that keeps you locked in.
Fitted — A slimmer, athletic cut that allows total mobility but eliminates the bulk of extra fabric.
Loose — Fuller cut for complete comfort, total range of motion and greater breathability.
Waist — Measure around your natural waistline. Be careful not to squeeze too tight to allow give.
Hip — With your feet shoulder width apart, measure around the fullest part of your hips to ensure you will have enough room to move comfortably.
Tall Sizes — All tall sizes are 2" longer than regular sizes.
