| Year | 2004 |
| Date | 10-Dec |
| Volume | 193 |
| Issue | 4,236 |
| Page | 681 |
| Category | General |
| Part | |
| Title | O-Ring Non-Return Valves |
| Author | Ron Bignell |
| Notes | Describes a neat variation on the usual ball type clack valve. Main body, side feed, valve seat, end cap, valve bobbin, assembly |