| Number | Name | Date | Kind |
|---|---|---|---|
| 2927609 | Vander Lans | Mar 1960 | |
| 4445542 | Fouss et al. | May 1984 | |
| 4449584 | Christensen | May 1984 | |
| 5234034 | Lyon | Aug 1993 | |
| 5322653 | Muller | Jun 1994 |
| Entry |
|---|
| Product Brochure, Cherne Industries Incorporated, 1990, p. 1 "Multi-Size Test-Ball Plugs". |
| Product Brochure, Cherne Industries Incorporated, 1993, p. 1 "Long Test-Ball Plugs". |
| Product Brochure, Cherne Industries Incorporated, 1992, p. 1 "Field Replaceable Sleeve Muni-Ball Plugs". |