These cassettes will be “too small” for any modern cassettes and require the use of a spacer.  In a ten going on eleven speed world you might wonder why anyone would use a sever speed cassette.

For starters, there’s more space between each cog, which not only makes friction shifting easier, it makes indexed shifting less finicky.  Less cogs also means its easier to find a cassette which allows for a better chainline in the gears you use most of the time.  Sometimes less is more.

A 13-30 will work will short cage rear derailleurs and a double crankset, even if the manufacturers’ specs say the short cage derailleurs will only work with a 27 or 28 tooth max cog. A 13-30 and reasonable chainrings will give you a gear range that works for every type of riding except for racing.  If you’re using this cassette with a triple, you’ll need a long cage derailleur.

Sadly, Shimano no longer makes the 13-30 HG70 silver 7 speed cassette.

Shimano HG50 7spd 13-30