What is the length and width of this bag?
Lying flat it is about 17"x6". It creates about a 3-4" diameter (circular) area when you fill it. It is meant to cover only the bands to protect them against abrasion, UV rays, & wear/tear. There is a grommet in the end that the spear tip goes through and then the bands rest in the sock. I've got (3) 5/8" bands on my 53" long JBL Magnum Sawed Off XHD speargun and it works great! Just bought another sling sock for a buddy.
Laid out flat, it measures 18 x 5 1/2 inches
This is 18-inches by 6-inches.
Unable to measure at this time since my spearguns are all packed up, BUT suffice it to say that I have one on my 140cm Mako (the longest gun currently available without going into special ordering),blue water type speargun, and it covers the 16mm x2 bands nicely, thanks to the drawstring. IF you're looking for the measurements in order to fit the sock on something else, I can't help you there right now.