220 Spa disconnect panel
Interesting.  What you actually need is a junction box with appropriate splices. 

However, as I sit here trying to price that, I have quickly discovered you aren't gonna get that for $11.  Splicing #6 wire is actually fairly hard.  Too big for wire nuts except a rare few (Ideal 454 blue), and on the super low end of the working range of Polaris connectors, which are expensive.  It seems the most popular method is split bolts (which are all bare metal) and great gobs of electrical tape.  One person buys a $5 accessory ground bar for a panel, and cuts it into 2-screw sections. (Note these ground bars accept Al wire, so it's an efficient way to bond Al to Cu). Again with gobs of electrical tape. 

You'll need to add an outdoor junction box and watertight(ish) entry grommets. 

So if economies of scale lead someone to offer a 4-wire splice block inside a junction box with a disconnect too for $11... good on them. 

Just one thing. Get a metal one.  A plastic outer box is for the birds. Under arcing, plastic will melt; steel will dissipate the heat. 

And understand those pull-out disconnects are super cheap, and not really intended to be ever operated. So if your plan is to never operate it, that'll be perfect.