Are these all momentary switches? need spst black contura ii switch w/illuminated red not momentary,

As long as you get one that say off-on it will not be momentary. DO NOT get the switch with ( ) as this means the switch is momentary example off-(on).

what are the exact opening dimensions needed for this product to fit in a pannel?

Per the Blue Sea Systems Website the cutout dimensions are: 0.83" Wide by 1.45" tall or 21mm x 37mm.

Why are the product descriptions and labeling so confusing? I had to look up with the 4-letter acronyms are in the listing, and I still have no idea.

I understand the confusion of seeing the designations such as SPDT, DPDT, SPST, DPST etc. These designations refer to the type of switch that you are purchasing. The very simplest version is SPST - Single Pole, Single Throw and is listed as simply ON / OFF in function. Each "pole" refers to the number of circuits that are being turned on or off. So a Single Pole (SP) has just one set or pair of connectors. You would use this on the Red Lead of a power supply for example to turn one thing on or off. Double Pole (DP) has TWO PAIR (4 Connections) that turn TWO circuits ON or OFF at the same time. Next comes the Single Throw or Double Throw designation (ST or DT portion of SPST or DPDT). This refers to whether the switch does more than just have an off / on function. A single throw (ST) IS Just ON / OFF. But Double Throw means you can have TWO functions controlled by single source of power. Good examples of this are what they call "Three Way Switches" on lights in your home. If you have TWO switches that can turn on /off the hall lights from two different locations you are using Double throw switches - not just ON / OFF but ON / OFF when the two switches are in the same or opposite positions. So a Single Pole Double Throw switch will have 3 connectors - middle is common and the two outer ones are connected to the center depending on switch position. A Double Pole, Double Throw Switch has 6 Connectors - 3 for each of two circuits. Making things more interesting is that there are switches that have a "center off" position that allow the switch to move from ON Down to Off Center to ON Up. If all you want is to turn something ON Or OFF just choose an SPST switch with no special center position and you are set to go. Take note that if you want that light on the switch to come on when the circuit is ON, you will need to wire the switch to provide power for the LED in the switch as well. Blue Sea provides "schematics" or wiring diagrams for all of these switches when you purchase them and you can also find details on their website.

Operation Mode	ON OFF
Current Rating	20 Amps
Operating Voltage	24 Volts
Contact Type	Normally Open
Brand	Blue Sea Systems
Terminal	SPST
Item dimensions L x W x H	4.38 x 2.69 x 1.75 inches
Circuit Type	1-way
Actuator Type	Rocker
Contact Material	Phosphor Bronze
International Protection Rating	IP54
Number of Positions	1
Upper Temperature Rating	85 Degrees Celsius
Controller Type	Manual Switch
Control Method	Touch
Connectivity Protocol	X-10
Color	Black
Wattage	240 watts
Number of Items	1
Manufacturer	Blue Sea Systems
UPC	632085079291
Item Package Dimensions L x W x H	3.82 x 2.6 x 1.77 inches
Package Weight	0.05 Kilograms
Item Dimensions LxWxH	4.38 x 2.69 x 1.75 inches
Item Weight	0.08 Pounds
Brand Name	Blue Sea Systems
Warranty Description	Warranty
Model Name	7929
Suggested Users	unisex-adult
Part Number	7929-BSS
Style	Spst, Off-on
Included Components	Great Product
Size	One Size

Contura II OFF-ON SPST Switch, Black

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