Many equine dentists recommend a straight bar Weymouth bit because it takes up less space in the horse’s mouth.

Sprengers French Weymouth is slightly rounded to make the bit lie well on the horse´s tongue. The shape on this weymouth makes the mouthpiece be stable and fit the horse with little space in the mouth. 

As the horse's mouth narrows downwards and the bridoon bit is placed below the weymouth bit, Sprenger recommends that the weymouth bit should be 0.5 to 1 cm shorter than the bridoon and that the shanks of the weymouth bit should be close to the horse's mouth for best stability and impact.