Written and maintained by CASRAI Editorial Board
Last updated
General equipment information, not medical advice. Anyone starting an exercise or rehabilitation program should follow the advice of a physician or health professional.
Short answer
A BOSU ball is a half-dome balance trainer: an inflated dome fixed to a rigid flat platform, usable with either side facing up. BOSU is the manufacturer’s brand, and the company says the name stands for “BOth Sides Utilized.” The manufacturer’s current product name is Balance Trainer, and it confirms that “BOSU ball” is the original name for the same product.
Definition and scope
The manufacturer’s FAQ answers the naming question directly: a BOSU ball is the same as a BOSU Balance Trainer, and “BOSU ball” is not a nickname but the original name, from when it was the only product the company sold. As the brand grew into a range of equipment, the dome-and-platform product took the name Balance Trainer. The “both sides” in the name refers to the two working surfaces: dome side up, or platform side up.
The manufacturer’s product page for the Pro model describes it as used in fitness, sports conditioning and rehabilitation facilities, and as designed for commercial use by personal trainers, physical therapists and fitness instructors. In an athletic training room, it sits with other small rehabilitation tools; the NFHS list summarised in our athletic training room equipment guide names BOSU balls beside balance boards, resistance bands, foam rollers and stretching mats.
How it is used in practice
This page covers the equipment, not exercise programming. Three points in the manufacturer’s FAQ matter to anyone who owns, inflates or supervises a unit:
- Inflation. The FAQ says to inflate the Balance Trainer until the dome is 8.5 inches high, and not to exceed 10 inches. The Pro product page likewise lists a height of 21.6 cm (8.5 in) “when properly inflated.” The FAQ adds that the dome should give a little under a person.
- Which side to stand on. The manufacturer states that standing on the platform side is not recommended, and that this warning is stamped on the bottom of the unit.
- Storage. The manufacturer says stacking units so the dome touches the black base of another unit can draw oil out of the dome. It describes the oily residue as normal and as removable with mild cleaner.
Types and sizes
People searching for BOSU ball sizes are usually comparing models. The manufacturer’s comparison page lists these Balance Trainer models and sizes (size in cm, as listed there):
| Model | Size | Manufacturer’s stated use or note |
|---|---|---|
| Home | 65 cm | Home gym use |
| Pro | 65 cm | Professional and commercial use; maximum user weight 350 lb (159 kg) |
| NexGen Home | 65 cm | Listed at 65 cm |
| NexGen Pro | 65 cm | Professional and commercial use |
| CorLok NexGen Home | 65 cm | Listed at 65 cm |
| K-Series | 55 cm | Described as “easy for travel” |
| Sport | 50 cm | Described as the manufacturer’s smallest Balance Trainer |
Most listed models are 65 cm. The 65 cm Pro model is 25.5 inches in diameter, weighs 7 kg (15.4 lb) and has a maximum load of 159 kg (350 lb), according to its product page. Models marked Home and models marked Pro are separated by the manufacturer’s intended-use labels, not by size, so a facility should read the stated use and load limit for the specific model.
Where it matters for labs, clinics and facilities
For a rehabilitation or athletic training room, the manufacturer’s own statements translate into a short facility checklist. Each line is the manufacturer’s statement, not a CASRAI recommendation:
- Model’s stated use: Pro is labelled for professional and commercial use; Home is labelled for home gym use.
- Maximum load: 350 lb (159 kg) for the Pro model; the other models’ limits are on the manufacturer’s own pages.
- Dome height when inflated: 8.5 in, not above 10 in.
- Platform side: standing on it is not recommended.
- Storage: avoid stacking a dome against another unit’s black base.
Equipment lists for other settings are in our sports medicine clinic supply checklist, youth sports team medical kit checklist and sports stadium medical facility supply checklist. For a related rehabilitation measuring tool, see what a goniometer is.
Common misunderstandings
- “BOSU ball” is not a different product from the Balance Trainer. The manufacturer says they are the same product.
- BOSU is a brand, not a generic word. Other manufacturers’ dome trainers are not covered by the figures on this page.
- The size is not the dome height. A 65 cm model is about 21.6 cm (8.5 in) high when inflated to the stated level.
- Both sides can be used, but not equally. The manufacturer’s warning about standing on the platform side applies even though the name says “both sides.”
FAQ
What does BOSU stand for?
The manufacturer says BOSU stands for “BOth Sides Utilized,” referring to the dome side and the platform side.
What sizes does a BOSU ball come in?
On the manufacturer’s comparison page, most models are 65 cm, the K-Series is 55 cm and the Sport model is 50 cm.
How high should a BOSU ball be inflated?
The manufacturer says to inflate the dome to 8.5 inches high and not to exceed 10 inches.
Is a BOSU ball the same as a Balance Trainer?
Yes. The manufacturer says “BOSU ball” is the original name and Balance Trainer is the product’s current name.
Sources
- BOSU, Frequently Asked Questions, checked 2026-10-30.
- BOSU, Compare Balance Trainers, checked 2026-10-30.
- BOSU, BOSU Pro Balance Trainer product page, checked 2026-10-30.
- NFHS, Essential equipment for a secondary school athletic training facility, checked 2026-10-30 (cited in the athletic training room equipment guide on this site).
