The 639 is a simple swivel base for main and jib sheets on very small boats or for control lines on boats of all sizes.
| Height | 75 mm | 1 15/16 in |
| Weight | 259 g | 9.14 oz |
| Minimum line Ø | 3 mm | 1/8 in |
| Maximum line Ø | 12 mm | 1/2 in |
| Fastener spacing | 26 mm | 1 1/32 in |
| Fasteners | M5 FH | #10 FH |
| Maximum working load | 136 kg | 300 lb |
