Would I still benefit from say three keywords:
Mattress size 3.5 feet
Mattress size 5 feet
Mattress size 6 feet
if I created a hybrid like this:
"mattress size 3.5, 5 and 6 feet"
or "the power" would dissolve?
Thank you.
as
@nanavlad said: a keyword like that will rank easily because it has no competition, but it also has no search volume, which means that even if you rank #1 for that keyword you'll barely get any traffic.
Put yourself in the shoes of your customer: would you ever look up "mattress size 3.5, 5 and 6 feet"? You wouldn't (I mean, I wouldn't)
People are either interested in mattresses size 3.5, size 5 or size 6, not all these 3 sizes combined. Which is why it's better to just create a product page on your site that's simply called "mattresses" and then add some filtering options (ecom plugins / software usually come with filtering options by default) on that page so that people can filter out whatever they want.
But a keyword like "mattresses" would be helluva competitive, I won't even look it up in SEO tools because, in general, 1-word and 2-word keywords are extremely tough to rank for, regardless of their intent. And they're even more competitive if they're commercial keywords like "mattress", or "buy mattress", or "purchase mattress", or "cheap mattress", or "buy cheap mattress"...
That's why, a much better way of going about ranking for that keyword would be to create a page that targets a medium competition keyword, or if a medium competition keyword is hard to find, then target a 3-word / 4-word long keyword containing the word "mattress", such as "normal size mattresses", or "3.5 feet mattresses for kids", or whatever (you will have to do your keyword research to find keywords that are not very competitive but which are also related to the products you're selling) and then optimize that page for this keyword ("normal size mattresses", or "3.5 feet mattresses for kids", or whatever keyword you're gonna find)
And an even better option - given the nature (ie. competitive) of most ecom keywords - would be to create a blog on your domain, throw the word "mattress" into an SEO tool (preferably Ahrefs, but other tools can work, too) and find 10-20 long tail keywords that are informational in nature and which talk about mattresses (and if they're also having monthly searches that would be even better), and then create some content around those keywords with the goal of informing (read: educating) people on the pros and cons, or advantages / benefits, or little known facts about the types of mattresses that you're selling and then add a link inside the content that takes your visitors to your shop in case that you've (presold them on your mattress and) they want to buy one of those mattresses.
