Wallach Flexsound Intrauterine Sound 920008. The Flexisound Intrauterine Sound is a sterile, single-use only instrument. It is made of white, gentle but firm, malleable plastic and can be curved between the thumb and finger and shaped for following the curve of the cervical canal. Graduations are in centimeters allowing for measurement of the uterine cavity. Wallach Disposable Intrauterine Sound is used in place of a reusable silver malleable or stainless steel sound. The intrauterine sound is used to gauge the depth and position of the uterine cavity. It is also helpful with the replacement of IUD's and verification of HSG procedures. The proximal portion of the sound is 3.5mm in diameter tapering to 12.5mm at the distal portion with a tip of 2.9mm. 25/BX. Price per box. FREE Shipping!