Butterfly expanders
Butterfly
— an expander of this type consists of two halves connected by a spring-loaded swivel mount. When working with a projectile, these halves converge and diverge like butterfly wings, hence the name. Such expanders work in compression, they are used to work out different muscle groups — in particular, the inner side of the thigh, shoulder and chest girdle, as well as the press. Among other things, "butterflies" are considered a good option for those who need to lose weight.Separately, we note that you should not confuse "butterflies" with tubular expanders (see the relevant paragraph), which have the shape of a figure eight.