The Toros Kaelatugi suurus 710 - 3 is size 3 with a 10 cm collar height and is described as intended for adults. Height is the main fit dimension mentioned in the product information, so it is not the same as the circumference of your neck — if you need to know whether the collar goes fully around, you should compare it with your own measurement or try it on.
The general rule with orthopedic collars is that the foam should sit comfortably against the underside of the jaw and the base of the skull, without pressing into the throat when you swallow and without leaving a large gap at the front. When fastened, you should be able to breathe and speak normally. The collar should limit sudden movement, but it should not feel painfully tight, and the skin underneath should not become red or irritated after a short trial.
Because height is the only size detail provided, the 10 cm version is best suited to someone with a medium-to-longer neck length. If you are on the borderline, it is worth trying the collar while sitting upright in a neutral position, not lying down, because a reclined posture changes how the collar sits. If the front edge pushes your chin upward or the back edge digs into your shoulders, the size is probably not right. In a typical adult collar, a height that roughly matches the distance from the jaw to the collarbone gives the most stable positioning.
When in doubt, ask a physiotherapist or the person who recommended the collar to check the fit. A collar that is too high can overextend the neck, and one that is too low may simply slide down. The key is that it holds your head in a neutral, comfortable posture rather than forcing it forward or backward.