| Keyword | CPC | PCC | Volume | Score |
|---|---|---|---|---|
| what were vacuum tubes made of | 1.95 | 1 | 9571 | 7 |
| how are vacuum tubes made | 0.57 | 0.3 | 6710 | 34 |
| what are vacuums made of | 1.96 | 1 | 2946 | 38 |
| vacuum tube material used | 1.81 | 0.3 | 9689 | 44 |
| what are vacuum tubes | 0.9 | 0.3 | 8714 | 91 |
| us made vacuum tubes | 0.54 | 0.4 | 1846 | 88 |
| history of vacuum tubes | 1.02 | 0.1 | 7872 | 23 |
| list of vacuum tubes | 0.48 | 0.8 | 6872 | 18 |
| pictures of vacuum tubes | 1.06 | 0.5 | 4331 | 53 |
| what materials can be vacuum formed | 1.78 | 0.5 | 9633 | 83 |
| description of vacuum tube | 0.45 | 0.4 | 5109 | 6 |
| invention of vacuum tube | 0.35 | 0.9 | 8335 | 84 |
| how did vacuum tubes work | 0.98 | 0.5 | 2755 | 82 |
| vacuum tube invented by | 0.05 | 1 | 8013 | 83 |
| what's a vacuum tube | 1.71 | 0.8 | 920 | 94 |
| how to make a vacuum tube | 1.61 | 0.8 | 7692 | 67 |
