I purchased a few of these several years ago. They have since been discontinued but its the only bandstacked C-band lnb I have come across. Useful for testing bandstacked settings on receivers. Another benefit is you don't have to switch voltage so you can potentially split the signal to multiple receivers. I haven't been able to test the sensitivity vs other lnb but the performance has been satisfactory. From what little testing I have done against it a DMX741 slightly outperformed it. Here are some specs:

Special for Digital C-Band Satellite Reception
Extended Frequency 3.7 GHz ~ 4.2 GHz
Bandstacked LNBF
L.O. Freq 5750
High Gain Output
Light Weight Design
100% Waterproof
Scalar Ring is not included. Fits on a standard Scalar Ring
Model Number B1SAT STACK
I/P Frequency 3.7-4.2 GHz
O/P Frequency 950-2050 MHz
LO Frequency Lower Band 5.15 GHz, Upper Band 5.75 GHz
Output Connector Type "F" Female Connector
LO Initial Accuracy ± 1MHz @ 25° C
Stability (-35°C to +52°C) ± 2.0 MHz
LO Phase Noise -60 dBc/Hz (@1kHz)
-80 dBc/Hz (@10kHz)
-90 dBc/Hz (@100kHz)
Noise Temperature 17 °K
Crosspol Isolation 20 dB
Conversion Gain 62 - 68 dB
Gain Flatness ± 0.5 dB /27 MHz
Image Rejection 40dB (min.)
Third Order Inter modulation -50 dBc (min.)
1 dB Compression Point 0 dBm
DC Voltage 10 – 24 VDC (supplied by receiver through coaxial cable)
Output Impedance 75 W F-Female
Output VSWR 2.5 : 1