Key design elements in my putter:
1. Round grip - 3"
2. heavier than standard (365 grams +)
3. counterbalanced
4. black head - no markings (no dots, lines etc.)
5. slant hosel
6. milled face
7. smaller than standard mid-mallet head
8. perimeter weighted
9. BGT shaft
(treatment for OCD on this subject)