Used one for years, considering upgrading to pic related for wider pullups
Thoughts on these
Isaac Sanchez
Owen Gomez
I found putting a chair next to mine helps. Do as much as you can unassisted and then finish up by assisting yourself as little as possible with your legs on the chair.
You can also start in an upward position standing on the chair, walk off, and then slowly lower yourself, but i ended up hurting my shoulder doing this so your mileage may vary.
Logan Nelson
If you have high ceilings and space you can buy a tower like below.
Joseph Garcia
they're good but don't get the cheapest one money can buy. Get a sturdy one and you can put gymnastic rings on it. (you can on the weak ones too but it'll warp it doing stuff like support hold but ring rows and ring pushups will probably be fine.