I recently made three separate purchases of these bags from Raygar, via Amazon, in sizes 90x50, 130x90 and 100x80.
I found them all easy to easy to use. Although the instructions appear comprehensive , they are missing some small but essential details . There are two removable caps; the large outer one is a securing ring that retains the transparent plastic valve membrane . Prior to deflating the bag you need to check that the membrane is centred (covering the hole) , before securing it with the larger ring . Then you are ok to suck the air out with a vacuum cleaner, before inserting and tightening the smaller stopper. I've found it best to use the lowest setting on the vacuum and to pause part way through the process , to reshape and flatten the bag and contents, making it easier to store.
For practicable everyday use, I'd recommend the 90x50 and 100x80 sizes. Blankets and single quilts will fit in the former, but for large double or king size, you'll need the 100x80. So far I've found only limited used for the very large 130x90 size, such as for storing garden furniture cushions.
Once packed and stored I remove and store the blue plastic `zip fastener' clips as they are easily knocked off and lost. Apart from these minor observations, I'm generally very pleased with the design and quality of this product.