Period / Incontinence pants- Swim bikini

Our leakproof Swim Bikini is the perfect swimming protection for periods, whether swimming in the sea, pool, or simply chilling poolside. Made with the same reliable built-in tech used across our period underwear range, so you can feel confident that you’ll stay leak-free. Our outer material allows water to simply roll off, keeping you fresh and dry all day long, whether you’re going for a dip or simply laying poolside. Absorbs 2-3 tampons worth.

Fit's slightly snug and we recommend sizing up if you are in between sizes.

Soft, Stretchy and Comfortable
Lightweight and super quick-drying
OEKO-Tex Certified Materials

Sizing: Swipe through the images to see Flux's size guide, with waist and hip measurements in centimetres. We currently have sizes XS-XL available, which covers UK 8-16/18. However, we are hoping to increase our size, flow and style range in the future. Let us know if you'd like us to stock something else at hello@youunderwear.com!

Garment Care:

Machine wash max 40°C with mild detergent, hang to dry. No bleach. No tumble dry.

BODY:86% Recycled Nylon, 14% Elastane
GUSSET LINING:100% Polyester
GUSSET:100% Microfibre, Biodegradable TPU

Our underwear has no added PFAS, and has been successfully tested for harmful substances and certified according to STANDARD 100 by OEKO-TEX®️.

View our sizing charts below. If you're in-between sizes, we recommend sizing up for comfort! If you need more specific sizing help, please email us at help@youunderwear.com.

Bralette / More supportive bra / Women's knickers / Men's trunks / Girls' bralettes / Girls' knickers / Loungewear

How to Measure Yourself

Chest band: wrap the tape measure around your body, just under your bust.

Bust: measure the fullest part of your bust.

Waist: measure around your body approximately 5cm below your natural waist where the waistband of trousers normally sit.

Lower hip: wrap the tape measure around the fullest part of your hips and bottom.

Two-Way Strap Bralette:

Bralette Size	UK	Band Width (in)	Band Width (cm)	Fits Bra Sizes (Approx)
XS	8-10	27"	68.5	30 B/C/D - 32 A/B/C
S	10-12	29.5"	75	32 B/C/D - 34 A/B/C
M	12-14	32"	81	34 C/D - 36 A/B/C
L	14-16	34.5"	87.5	36 C/D - 38 A/B

More Supportive Bra:

Bra size	Chest band measurement (inches)	Approx. cup sizes	Approx. UK dress size
Small	28-30"	B, C, D	8- 10
Small +	28-30"	DD, E, F	8- 10
Medium	32-34"	B, C, D	12-14
Medium +	32-34"	DD, E, F	12-14
Large	36-38"	B, C, D	16-18
Large +	36-38"	DD, E, F	16-18
Extra large	40-42"	B, C, D	20-22
Extra large +	40-42"	DD, E, F	20-22

Women's Thongs, Bikinis, and Boy Shorts:

UK Sizes	EU Size	Waist (in)	Waist (cm)	Hips (in)	Hips (cm)
6	34	23-24	58.5 - 61	33	84
8	36	25-26	63.5 - 66	35	89
10	38	27-28	68.5 - 71	37	94
12	40	29-30	73.5 - 76	39	99
14	42	31-32	78.5 - 81	41	104
16	44	33-34	83.5 - 86	43	109
18	46	35-36	88.5 - 91	45	114
20	48	37-38	93.5 - 96	47	119
22	50	39-40	99.5 - 101	49	124

Men's Trunks:

Size	Waist (in)	Waist (cm)	Clothing Size (approx.) (in)	Clothing Size (approx.) (cm)
XS	29-31"	74-79	28-30"	71-76
S	31-33"	79-84	30-32"	76-84
M	33-35"	84-89	32-34"	84-89
L	36-38"	91-97	34-386"	91-97
XL	39-41"	99-104	36-38	91-97
XXL	41-43"	104-109	38-40"	97-109
3XL	43-45"	109-114	40-42"	109-114

Girls' Bralettes:

We feel that there isn’t a set size for bodies at different ages, and we don’t want to put any additional pressure on young girls, so our sizing looks a little different. We have 4 sizes, all named after Ugandan towns! We suggest using band width as a starting point, although do get in touch if you have any specific sizing questions.

Size	Band Width (in)	Band Width (cm)	Fits Ages (Approx.)	Worn By:
Jinja	23	57-58	9-10	Hollie & Amelia, age 9 1/2, band with 23"
Kira	25	63-64	10-11	Help us fill this in ...
Lira	27	68-69	11-14	Liv, age 11. Phoebe & Flora, age 11 1/2. Lana, age 13 1/2, 69cm band width, wears 30B/XS. Beth, age 14.
Masaka	29	73-74	13+	Hannah, 32C

Girls’ Knickers:

Details	Waist (in)	Hips (in)	Ages (Approx.)	Women's equivalent size
Jinja	22-23.5”	25-27”	7-9	4 (EU 32)
Kira	24-25”	30-32”	9-11	6 (EU 34)
Lira	25.5-27”	34-35”	11-13	8 (EU 36)
Masaka	27.5-28.5”	37.5-38.5”	13+	10 (EU 38)

Pyjama bottoms:

Our PJs are designed to be unisex, so the sizing is a bit more flexible with an elasticated waist, cord drawstring and also longer leg length.

Details	Women's sizing (UK)	Men's sizing
XS	6-8-10	28-30" waist
S	10-12-14	30-32” waist
M	14-16-18	34-36” waist
L	18-20-22	38-40" waist

- Stretch-blend organic cotton
- 95% GOTS Certified organic cotton, 5% elastane
- Pre-washed, shrink-resistant fabric

Machine wash, do not tumble dry - we suggest the eco-conscious choice of 30°C.

£2.25 for single items, £3.95 for sets and packs

Free shipping on UK orders over £60
All items posted Royal Mail's Tracked 48 service
International Shipping information is available here

We offer a happiness guaranteed return policy. If you are unhappy for any reason, we offer a fuss-free exchange or refund on all unworn and unwashed items within 30 days of purchase.

Orders over £60 qualify for free UK delivery

Fuss-free exchange or refund on all items within 30 days of purchase

Period / Incontinence pants- Swim bikini - Moderate Flow

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