Shure A15AS In-line Switchable Attenuator 15 Inch Crash you snap the cover plates

you snap the cover plates back in place

Cardioid pattern

Classic styling with Celestion Blue Alnicos speakers make this a great extension cab for the AC30 or any other amp you connect it to

which may cause stress on the PC board assembly while the outside bookend cover provides a protective zone for the switches

noise level ITU-R BS

Shure A15AS In-line Switchable Attenuator 15 Inch Crash you snap the cover platesThe Shure A15AS Switchable In Line Attenuator reduces the level of any balanced microphone or line level signal by 15, 20, or 25 dB. It is specially suited to reducing the level of a high output microphone to prevent it from overloading the microphone input of a mixer or recorder in applications with high sound pressure levels. In addition, the A15AS may be used to reduce the level of a line level mixer output to prevent overloading the aux level