This is a replacement joystick knob for a large variety of different powerchairs. The rainbow effect is slightly different on each skull making each one unique. They will match the listing photos closely, but not perfectly. The joystick is about the size of a pool/billiards ball and is sized to be ergonomic and comfortable. We have other colors available in our other listings. The hole is 1/4″ in diameter; however, if you need a different hole diameter, please let me know. I can adjust it. There is a screw on the back of it, so it can be tightened. We can confirm fitment on the following models; however, you should still measure the joystick shaft to make sure it is ¼” before ordering. Permobil F3, Permobil F3 Corpus, Permobil F5, Permobil Koala, Permobil M3, Permobil M3 Corpus, Permobil M5, Permobil M300, Permobil 300, Quantum 3, Quantum Edge 3, Quantum Q6, Quantum Q6 Edge, Quantum Q6 Edge 2.0, Quantum Edge 2.0, Quantum Stretto Q-Logic 3, Quickie 646, Quickie 636, Jazzy Passport, Jazzy 7, Jazzy HD, Terra/Terra SX B+B Enjoy Mobility, Air Hawk Power Chair, Alltrack HD/HD3, Vive Mobility Foldable Long Range Transport Aid, MobilityPlus+ Ultra-Light, Invacare TDX SP, Scewo Bro, Fold&Go MagshockThis was heavily remixed from a model created by Thingiverse user trailogy, and is licensed under cc-sa. Skull by trailogy on Thingiverse: https://www.thingiverse.com/thing:518109 I can custom make all kinds of joysticks, if you would like something made please message me.