The below measurements are approximate and are for the tallest point of each ring:

• The Ankh design measures 9.6mm tall
• The Pegasus design measures 9.8mm tall
• The Elephants design measures 3.7mm tall
• The Skull and Crossbones design measures 6.3mm tall
• The Daisy Chain design measures 6.3mm tall
• The Claddagh design measures 8.2mm tall
• The Butterfly design measures 7.1mm tall
• The Floral design measures 5.8mm tall
• The Infinity design measures 4mm tall
• The Petunia design measures 4.8mm tall
• The Triquetra design measures 7.4mm tall
• The Band Design measures 2mm tall 
• The Black Onyx design measures 6.5mm tall
• The Gecko design measures 7.6mm tall
• The Ripple design measures 4.3mm tall
• The Braid design measures 3.7mm tall
• The Sleek Point design measures 4.5mm tall
• The Twisted Wave design measures 5.4mm tall
• The Triple Peace Sign design measures 6mm tall
• The Flower Crown design measures 2.3mm tall
• The Hollow Heart design measures 7.7mm tall
• The Beaded Point ring measures 3mm tall

More rings are available here.