Jawzrsize and HYOIDR are marketed for the same thing but train different muscles that produce opposite cosmetic outcomes.
Jawzrsize is a silicone ball you bite. It loads the masseter on the side of the face, which is the muscle that closes your jaw when you chew. Trained masseters get bigger, and bigger masseters widen the lower face.
HYOIDR is a breathing resistance device. It loads the suprahyoid muscles under the jaw, which are the muscles that lift the hyoid bone. Trained suprahyoids pull the underside of the jaw taut and sharpen the jaw-to-neck angle.
If you want a wider, more square-looking lower face, Jawzrsize is on-target. If you want a sharper visible jawline and a defined jaw-to-neck angle, Jawzrsize is training the wrong muscle group. HYOIDR is designed for the second goal.
The second difference is joint safety. Jawzrsize applies bite pressure through the front teeth, which loads the temporomandibular joint (TMJ). Long-term users commonly report TMJ pain, tooth sensitivity, and enamel wear. HYOIDR uses breathing resistance and puts zero load on the TMJ.
Jawzrsize is a silicone spherical resistance ball. You place it between your front or back teeth and bite down repeatedly. It comes in three resistance levels (Beginner, Intermediate, Advanced). The training modality is repeated isometric bite contractions.
The muscle group loaded is the masseter (primary), the temporalis (secondary), and the medial pterygoid (tertiary). All three are jaw-closing muscles that sit on the side of the face and skull.
HYOIDR is a small handheld inspiratory resistance device. You place the mouthpiece between your lips and breathe in against calibrated resistance. It comes in seven resistance levels (progressively increasing spring tension). The training modality is repeated resisted inhalation.
The muscle group loaded is the suprahyoid group (mylohyoid, geniohyoid, digastric, stylohyoid). These sit under the jaw and lift the hyoid bone. Loading happens through the upper airway dilator reflex, a brainstem-mediated response to negative pressure at the upper airway.
Both devices apply progressive overload. That is where the similarity ends.
The visible jaw-to-neck angle (the cervicomental angle) is produced by two things: the shape of the mandible and the tension in the tissue underneath it. The mandible is set by bone. You cannot change it in an adult without surgery.
The tissue underneath the mandible is set by the suprahyoid muscles. When these muscles are toned and the hyoid bone is elevated, the skin and soft tissue under the jaw are pulled taut. That is the sharp angle people describe as a "defined jawline" or "good side profile."
The masseter has nothing to do with this. The masseter sits on the side of the face, running from the cheekbone to the angle of the jaw. Masseter hypertrophy widens the lower face and gives the face a more square appearance from the front. It has no effect on the jaw-to-neck transition at all.
This is a common category confusion. People see photos of men with strong-looking jaws and assume "bigger masseter" is the mechanism. Usually the mechanism is: low body fat, good posture, and toned suprahyoids. The masseter is often average size in these photos.
Jawzrsize applies load through the front teeth. The TMJ is a hinge joint between the mandible and the temporal bone. It was not designed for sustained, repeated, high-force front-tooth bite pressure. Chronic loading of the TMJ produces:
Independent case reports and dental clinical observations of these outcomes exist in the literature for chewing-based jaw trainers as a category. Jawzrsize's own labeling advises stopping use if you experience jaw pain.
HYOIDR uses inspiratory pressure, not bite pressure. There is no load on the TMJ at any point in the training. The mouthpiece is sealed around the lips, and the resistance is felt as an inhalation restriction. The teeth are not involved.
For anyone with existing TMJ symptoms, bruxism, or dental sensitivity, Jawzrsize is contraindicated. HYOIDR is not.
Masseter training evidence for cosmetic jawline improvement: limited and mostly anecdotal. The dental literature has extensive data on masseter hypertrophy in bruxism patients, and it consistently shows that a hypertrophied masseter widens the visible width of the lower face. This is the opposite of the "sharp jawline" outcome most Jawzrsize marketing implies.
Suprahyoid training evidence for jawline-relevant outcomes: substantial. Two decades of dysphagia rehabilitation research using CTAR and the Shaker exercise consistently show hypertrophy of the suprahyoid group and elevation of hyoid resting position within six to twelve weeks. Inspiratory resistance training (IMST) has 20+ years of research in sleep apnea and COPD showing measurable improvements in upper airway muscle activation, including the suprahyoid group.
Neither training modality has been studied specifically for cosmetic jaw-to-neck angle in trained young adults in a randomised trial, because that funding does not exist. The mechanism data, however, is well established.
If you want a wider lower face, more square jaw appearance, or you specifically want masseter hypertrophy: Jawzrsize is on-target, but expect the widening effect and expect the TMJ tradeoff.
If you want a sharper visible jawline, a defined jaw-to-neck angle, or a better side profile: Jawzrsize is training the wrong muscle group. HYOIDR is designed for this outcome.
If your goal is a stronger bite for functional reasons (elite athletic performance, singing, wind instruments): the masseter matters, and Jawzrsize can help. But this is a small use case.
If you have TMJ issues, bruxism, or dental sensitivity: avoid Jawzrsize entirely. HYOIDR is safe.
Jawzrsize retails for around $30–40 for a single ball or $60–80 for the three-level pack.
HYOIDR retails for €36 (one device with seven progressive resistance levels built in). €48 for the HYOIDR + Masseter Trainer bundle (a molar-positioned masseter trainer that avoids the front-tooth TMJ loading of Jawzrsize-style trainers).
Both ship internationally. HYOIDR ships free to the EU, UK, US, Canada, Australia, and New Zealand.
Can I use Jawzrsize and HYOIDR together?
Technically yes, but if the goal is a sharper jawline, Jawzrsize is working against you by widening the lower face. If you specifically want both a wider masseter and a sharper jaw-to-neck angle, use HYOIDR for the second goal and a molar-positioned masseter trainer (not a front-tooth ball) for the first.
Which works faster?
Neither is fast. Both operate on standard muscle adaptation timelines: neural adaptation in the first two weeks, early hypertrophy at six weeks, visible change in the six to twelve week window with consistent daily use.
Will Jawzrsize damage my teeth?
The dental literature and Jawzrsize's own labeling both note that front-tooth bite pressure can cause enamel wear and TMJ symptoms in some users. This is not universal but it is common enough to be a documented risk category.
Is HYOIDR just Jawzrsize with a different name?
No. They train fundamentally different muscle groups through fundamentally different mechanisms. Jawzrsize is a chewing-based masseter trainer. HYOIDR is a breathing-based suprahyoid trainer. The devices look nothing alike and produce different cosmetic outcomes.
What if I want a stronger bite specifically?
Chewing-based training does build masseter strength. If bite force is your actual goal (rare outside of specific athletic or clinical use cases), Jawzrsize does that. Just understand that a wider face is the cosmetic side effect and TMJ loading is the joint tradeoff.
This comparison is educational, not clinical advice. If you have existing TMJ pain or dental problems, consult a dentist before starting any jaw-loading protocol.