How to make your daughter's first period EASY and FUN!CLICK HERE TO READ.
Welcome to Knicked, Welcome to Puberty and Periods SHOP HERE
Terms & Policies
Please see each product page, for individual sizing.
As a general rule, please choose the same size for our period undies and period swimwear as your child's regular underwear size.
Our period underwear is designed here using Australian Child/Youth underwear guidelines. It's important to note that child sizing, also crosses over into women's sizing at our 12/14, so we have also shown this on our sizing charts (on each individual product page) to assist.
We also understand purchasing online can make judging sizing difficult and everyone has a different body shape (literally hundreds of waist & hip combinations) so we have created guides on each product page to help you choose the best fit for each product, or feel free to email our helpful team at theteam@knicked.com.au with waist & hip measurements so we can assist further.
To measure against existing underwear: use the flat lay measurement (side seam to side seam on the waistband) to compare with their current underwear.
Don't panic if you do find you've ordered the wrong size, KNICKED will happily exchange sizing and also cover the postal costs to reship (once per order) as long as underwear has been tried on over clean underwear and returned in AS NEW condition (not washed/worn free of lint/hair/marks), and packaging in original condition.
Please click here for our Exchange/Refund Forms & Guidelines to organise an exchange.
Knicked BFFs™ - Bestie Flow Friend
The World's First 2-in-1 Hybrid Period Undies
Swimming? Dancing? Unexpected period? School day?
We've got you covered.
Our Knicked BFFs™ are the ultimate SOS period solution - the world's first 2-in-1 hybrid period undies that work both in AND out of water. Wear them under your bikini, leotard, leggings, or even regular underwear for total leak-proof confidence anywhere, anytime.
💖 What Makes Them Different?
Unlike regular period underwear OR period swimwear, our BFFs feature:
✔ 2-in-1 hybrid design - works in water AND out of water
✔ Waterproof technology that blocks water from getting in
✔ Leak-proof protection that locks period flow from getting out
✔ High-cut, discreet design under any outfit
✔ Award-winning stop-leak technology
✔ Soft, slimline & seriously clever
✔ Compliant with Swimming Australia's Inclusive Swimwear Policy
That means one pair replaces period swimwear, dance undies AND heavy flow underwear - saving you over $80 and endless outfit changes.
🩰🏝️ Perfect For:
• Under swimwear at the pool or beach
• Under leotards for dance & gymnastics
• Under leggings, shorts & everyday clothes
• Emergency period protection at school
• Sleepovers & school camps
• Any activity where you need total confidence
🌿 The Ultimate Schoolbag Essential
Created by a mum, designed for real teen life.
Our BFFs are:
• Ultra discreet & comfortable
• Reusable & sustainable
• Budget-friendly (replaces 3+ products)
• Made to move with you
• Comes with a waterproof, odour-proof wet bag
Because periods shouldn't mean missing out on swimming, dancing, or living your best life.
Knicked period undies have always been and will continue to be FREE FROM NASTIES such as PUL'S (plastics) or PFAS (chemicals).

How to wear:
These aren't your average undies - pull them on, then up high at the sides so they sit snugly and low under the belly for the best protection.
Care tip:
Wash before first use. Each pair comes in a reusable, waterproof, and odour-proof wet bag – perfect for storing your BFFs in your bag or when they're wet, waiting for a wash. Less waste, more wow.

Our teen models are wearing a Teen 12/14 (adult 6 or 8).
Please use the flatlay measurements to compare to another brand or existing pair to select the correct fit and if between sizes or very tall we recommend sizing up.
Tracked postage is $9.95
Express postage is $14.50
Orders over $99 receive complimentary FREE REGULAR SHIPPING
Knicked will exchange item(s) that have not been washed, worn and are in AS NEW condition, we request you submit our Exchange Form within 14 days of receiving your product. Knicked will cover one new shipping cost as a gift to assist - please note: if purchased on sale or outside Australia item(s) can ONLY be returned for a gift voucher to repurchase a new size or style within 5yrs.
Oh wow what great undies surprised at just how well they work and the fit is just perfect they go really well with my swimsuits leggings and my netball shorts definitely no bulky panty lines showing I really recommend these amazing undies I am definitely purchasing some more
We were lucky enough to be given a pair to trial and have since purchased 2 more pairs one for my younger daughter and my niece. It's mind blowing to think one pair can do so much but they do, I remember my eldest got her first period the day before school swimming and while I had Knicked period undies on hand for this day we didn't have swimmers and sadly she had to sit on the sidelines and miss out - with these never again will a mum be unprepared! Even though we have tested them thoroughly I still don't know how it works but THEY DO.
Great fit.
Great for active girls. Love the hybrid style! Great quality and value. Excellent customer service.
Worked great under competition costumes. No leaks and never showed.
Bought these for my daughter to wear under her compulsory school bathers for lessons and swimming carnival.
My daughter loved these undies. Will definitely be getting more of these.
My teen saved up for a bikini she really wanted to wear at a NYE's pool party and of course disaster struck 2 days out!! Her friends told her about BFFs which arrived in time with express and while she was nervous (boy/girl party) - you could not see them under even the skimpy bikini and WORKED all afternoon and long into the night and she was quite heavy. Best product and service on the PLANET. Thank you so much Knicked.
Their shape is good but they are sized up So we bought 2 sizes and one will be for a few years time. (Ch 12-14 is more like an adult 8).Haven't had them long enough to use though.
Our second order of these amazing nickers they are just perfect for under our shorts and swim shorts they are so absorbent my daughter and I really enjoy them and also enjoy the new style nickers they are just perfect thank you so much .
Our second order of these amazing nickers they are just perfect for under our shorts and swim shorts they are so absorbent my daughter and I really enjoy them and also enjoy the new style nickers they are just perfect thank you so much .
Nice undies I really like these amazing undies nickers they fit so well and are super absorbent just perfect for under my shorts and swim shorts my daughter are really enjoying these wonderful nickers also enjoying our new style nickers the are just amazing nickers thank you so much Knicked
Good quality and well designed underwear. Fit my daughter very well, most importantly it works.
My daughter and I are just loving these amazing nickers we have given them five stars
10-12 which is what I buy in all her sizes in period u underwear is too small they are cutting into her legs so I have to return them
As a first time customer we understand sizing can differ between brands, to help with this we add flatlay in addition to total waist measurements to all our products which allow meausuring against any existing brand you have at home. All our swimwear/underwear has stretch which allows for these variations but our BFFs are different in that they need to create a perfect seal around the body to stop water entering when worn under bikini's/one pieces whilst swimming, so don't have the same stretch. Knicked will always cover ONE additional postage costs for any exchange and if you need sizing assistance, please reach out, we are here to assist.
Slimline and multipurposed. Perfect!
My mum bought these for me before heading to school camp where we were doing lots of water activities. The BFFs really do the best job! I wore them under my period swimmers to make sure I was protected and there was not one leak and I could forget that I even had my period and just have fun!! I've asked Mum to buy me another pair.
Great great great!!
excellent for school camp!! my very nervous girl had school camp which was also water based, these were brilliant as she could still wear her normal bathers and you couldn't see them as they are cut really high and slim at the hips. she said she wore them one day for 7hrs with no embarrassing moments so THANK YOU these are as they state a girls best friend!
My daughter absolutely loved the BFF 3in1's and this is all game-changer for being able to just wear normal swimwear/bikini. She has also now worn them under her leo for dance and you couldn't tell and both times NO LEAKS - wow just wow. Online buying another pair for my older teen as i type this..