Lips
Start rounded, as for "uu", relaxing slightly as the r takes over. The diagram shows the rounded start.
The American "cure" vowel: a rounded "uu" gliding into the r colour. It ends on a real r, unlike the British version that melts into "uh".
Example words: cure, tour, pure, sure, tourist

Start rounded, as for "uu", relaxing slightly as the r takes over. The diagram shows the rounded start.
Start high-back. Then curl the tip up and back, or bunch the mid-tongue, into the r. The tip never touches the roof of the mouth.
Medium. A short rounded "uu", then hold the r colour to finish the sound.
Say "tour" and hold the last sound. You should be able to sustain a steady "errrr" at the end with no tapping. If the ending is a soft "uh" that vanishes, add the r back.
Dropping the r so "tour" ends on a weak "uh" (that is the British version), or tapping and trilling the tongue. Hold the shape instead.
🔊 plays the app's native voice. 🎤 records you so you can play it back next to it. Your recording stays in your browser.