I be a long time Comcast hsus customer , have use the Motorola sb4100 and sb5101 cable modem for my DOCSIS 1 & 2 cable service . when DOCSIS 3 be implement in my area , I purchase the Motorola sb6101 cable modem direct from Amazon -lrb- not 3rd party vendor -rrb- as it be on the Comcast approve modem list . the product arrive in new condition and I swap it out with my old sb5101 modem , without any problem . I call Comcast hsus customer service and give they the MAC address of the new sb6121 modem and it be provision and online in less than five minute . the datum speed be stable and rock solid . very satisfy with this purchase from Amazon .