3.5mm to SMA adapters are extremely usefull in test labs. The 3.5mm is sometimes called a super sma: higher frequency performance, thicker wall, but very similar and compatible. 3.5mm's work to 37+ghz, precision sma's to 27ghz, so these 3.5mm to sma adapters are limited to 27ghz. SMA to 3.5mm adapters are usefull as connector savers, as even though properly made 3.5 & sma connectors mate, a bent sma pin will damage the 3.5mm female contacts as its air dielectric offers no support. Using an sma to 3.5mm adapter insures no mechanical compatibility issues exist.