Remember when tank covers were made in various sizes to fit tanks? You could get a Dye Rhino cover in 48ci, 68ci, 70ci, and 98ci sizes at least.
Problem is, tank sizes have been prone to variances in length/diameter as suppliers' stocks change over time (Ninja's made 45ci, 48ci, 49ci, and 50ci tanks). I have seen directly that retailers closing up shop have often had on hand an inventory of older tank covers in sizes that are no longer relevant (70ci peanut cover anybody?).
Which brings us to today. Tank covers are now made to be "universal" in terms of either being just a butt sleeve, simple stretchy neoprene, or something like this contraption with its kludgy velcro strips.
I understand why this is happening--retailers don't want to have to pay to keep a large inventory of multiple sizes and tank makers don't worry about adhering to standard dimensions. But as a customer, I miss the golden days of high density neoprene and urethane padded covers that provided way more protection. Just my $0.02...your mileage may vary.