Had a house built and ran wire for the spa disconnect which I understood at the time must be in the "vicinity" of the spa. Come to find out later, it must be "in the line of sight" of the hot tub. To get to line of sight, I need to make a 90 degree turn and run about 3 ft of flexible conduit (its a very short distance). However I still need to "tap" the existing wire already in the wall. Can you think of a reason I cannot use a 60a "on/off" non-fused cutoff switch (around $11 at Lowes) in between the true GFCI spa disconnect and this area where I inadvertently left the wire on an exterior wall for future use? I plan to padlock this 60a in-between switch so no one mistakenly thinks its the spa cutoff. I did some reading and they want the spa GFI cutoff in line of sight so if someone is working on the hot tub and sees someone turning on the breaker they can visually see them doing that.
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.
Is this wire to be tapped for another use or just extended to the proper place? If it's extended, no need for a cutoff at that location, just use a covered junction box. Since you're dealing with a spa & will be near water everything should be rated for outdoors/wet locations and must be properly grounded.