Soma Erect STF Impotence Pump. The SomaTherapy-ED SOMAerectStf represents the new generation of uniquely custom fitted vacuum therapy systems for restoring penile health. It offers 3 cylinder sizing options so you can precisely find the anatomically correct sizing option that neatly fits your fully rigid penis size. The custom sizing technology was developed to ensure that each patient receives the highest level of comfort when treating their ED. The custom sizing will prevent the loose non-penile tissue from around the base of the penis (supra-pubic fat or scrotal skin) from being drawn into the mouth of the cylinder during the creation of an erection. The use of the customizable system guarantees a much more comfortable erection experience every time.