The basic product, when it works, does its job with no problems. However, the earphone jack on my base plate failed, snapping off the base plate and breaking the wire to contact for the right earphone. When I contacted Sena about the problem and asked for support on a materials failure (the helmet was never dropped or bumped, ditto for the base plate), they said "no." I had to buy a new base plate even the mic and left channel work as they should. The phone jack simply isn't well supported. Plugging phones into the jack repeatedly eventually tweak the jack too much and... snap.
Also, the cable for an MP3 player makes no sense. The male connector goes into the base as expected. But the other end is a female socket while MP3 players expect a male plug. A short male to male cable will fix this but that means there are two cables involved where only one cable is required.
The base plate gets good rates for use (just talk and listen, what's left?), and sound clarity (the phones work just fine and the mic seems to work well, too). Installation is easy enough, too.
The problems with the earphone jack and the cable keep the base plate from getting a good "bang for the buck" rating (plan to buy at least one replacement some day - effectively doubling the cost of the base plate). Durability is OK except for the jack, making it a near deal-breaker. Nonetheless, I'll recommend buying this base plate because, if you have an SMH-10 or -5 main unit, and need to use earphones, there's not much choice here.
NOTE: Using earbuds or almost anything resembling earphones worn while operating any motor vehicle on a public road may violate a part of motor vehicle codes for your state or municipality. And even if it doesn't, LEO can still take exception to the idea if they're spotted during a stop (BTDT). Past that, any phones that work under a helmet will limit what you hear from outside the helmet (car noises, sirens, etc.), whether the phones are sound attenuators (ER-6i's, for example) or just cheap plugs with the volume turned up. Ride your own ride, but ride aware.