Best Period Underwear: TomboyX First Line Boxer Briefs, Trunks and Bikinis Compared
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Period underwear replaces or backs up pads and tampons with a built-in absorbent layer, and it's reusable. TomboyX's First Line comes in boxer briefs, trunks, boy shorts and bikinis for every body. Here they are compared by absorbency, rise and fit, with prices and 18% off for new customers.
Quick picks
| Best for… | Pick | Size | Price today |
|---|---|---|---|
| Heaviest days |  Bikini | up to 8 tsp | $26.00 $21.32 with our code |
| Boxer brief fit |  9" Boxer Briefs | 4-5 tampons | $38.00 $31.16 with our code |
| Mid-length |  4.5" Trunks | 4-5 tampons | $34.00 $27.88 with our code |
| Short and comfy |  Boy Shorts | 4-5 tampons | $29.00 $23.78 with our code |
| Best value |  Bikini 3-pack | 3 pairs | $66.30 was $78.00 |
TomboyX offers today
off
18% off for new customers (orders over $20)
Show codeoff
15% off for new customers
Show codeHow to choose period underwear
Best period underwear
TomboyX First Line Period Bikini
The most absorbent First Line style: up to 8 teaspoons (about 6-7 regular tampons) in a low-rise bikini.
TomboyX First Line Period 9" Boxer Briefs
TomboyX's signature boxer briefs with absorbency for periods, pee or sweat, for staying dry all day.
TomboyX First Line Period 4.5" Trunks
A mid-rise trunk with a 4.5-inch inseam and the same First Line absorbency.
TomboyX First Line Period Boy Shorts
Boy shorts with a 2.5-inch inseam, absorbing up to 4-5 regular tampons.
-15%TomboyX First Line Period Bikini 3-Pack
Three First Line bikinis for less than buying them one at a time.
-15%TomboyX First Line Period Boy Shorts 3-Pack
A 3-pack of First Line boy shorts at a lower price per pair.
Ways to pay less at TomboyX
FAQ
How much does period underwear hold?
TomboyX's First Line bikini absorbs up to 8 teaspoons (6-7 regular tampons); the boxer briefs, trunks and boy shorts up to 4-5 regular tampons.
Is TomboyX period underwear PFA-free?
Yes: TomboyX says First Line is PFA-free and OEKO-TEX certified.
Can you put period underwear in the dryer?
TomboyX says First Line is machine washable and machine dryable.
Do I still need a pad with period underwear?
Many people wear it alone; on your heaviest days TomboyX leaves room for a backup liner or winged pad.
Is there a TomboyX discount code?
Yes: new customers get 18% off orders over $20, or 15% off with a second code. Tap Show code in the offers box.
Product details and prices from TomboyX's website, checked October 14, 2026. Codes from TomboyX through our affiliate network and our TomboyX store page. Prices change; the final price is shown at checkout.