
Thimbles are indeed made of mild steel and then galvanised. Galvanizing is a process of applying a zinc coating to steel, typically via hot-dip galvanization, to protect it from rust and corrosion. Mild steel is a common base material for thimbles due to its strength and affordability.
G414 wire rope thimble, a type of rope thimble, is indeed used in aquaculture mooring to protect wire, fiber, or synthetic ropes from damage at the connection point of a mooring line.
Thimbles like the g414 provide a solid, protective element that prevents the rope loop from crushing and helps distribute the load.
G414 Rope Wire Thimble Diagram:

Specification of G414 Rope Wire Thimble:
| SPEC | Thickness (mm) | A (mm) | K(mm) | N(mm) | P(mm) | R(mm) | Weight(kg) |
| 1/8" | 1.2 | 46 | 33 | 28 | 17.5 | 3 | 0.012 |
| 3/16" | 1.2 | 46 | 34 | 28 | 17.5 | 5 | 0..12 |
| 1/4ʺ | 1.5 | 56 | 42.7 | 37.5 | 22 | 7 | 0.024 |
| 5/16" | 2 | 64 | 48 | 45 | 25.5 | 8 | 0.05 |
| 3/8" | 3 | 71.7 | 52.4 | 53.4 | 29.2 | 10 | 0.1 |
| 7/16" | 3 | 80.8 | 59.1 | 58.8 | 32 | 11 | 0.115 |
| 1/2ʺ | 3.5 | 87 | 62.6 | 70.3 | 39.7 | 13 | 0.19 |
| 9/16" | 3.75 | 96 | 72 | 69 | 38 | 14 | 0.22 |
| 5/8" | 3.5 | 103.7 | 78 | 78.3 | 45.9 | 16 | 0.265 |
| 3/4" | 5 | 124 | 91.3 | 95.5 | 53 | 21 | 0.53 |
| 7/8" | 5 | 135 | 102.5 | 103 | 58 | 23 | 0.645 |
| 1ʺ | 5 | 150.5 | 110.9 | 119 | 65 | 26 | 0.855 |
| 1 1/4ʺ | 6 | 170 | 125 | 134 | 75 | 28-32 | 1.4 |
| 1 3/8" | 10 | 222 | 150 | 165 | 87 | 36 | 3.52 |
| 1 1/2ʺ | 12 | 223 | 150 | 167 | 88 | 38 | 4.2 |
| 1 5/8" | 12 | 275 | 195 | 210 | 120 | 42 | 6.5 |
| 1 3/4ʺ | 12 | 300 | 230 | 205 | 120 | 44 | 6.6 |
| 2ʺ | 12 | 375 | 289 | 255 | 150 | 52 | 10 |
| 2 1/4ʺ | 16 | 445 | 310 | 283 | 170 | 58 | 18 |
| 2 1/2ʺ | 18 | 480 | 365 | 310 | 170 | 65 | 26.3 |
| 2 3/4ʺ | 18 | 500 | 360 | 340 | 175 | 76 | 29.18 |
| 3ʺ | 20 | 555 | 420 | 350 | 175 | 80 | 37.4 |
| 3 1/2ʺ | 20 | 625 | 483 | 375 | 200 | 90 | 44.9 |
4"
| 20 | 665 | 530 | 400 | 220 | 105 | 49.6 |
5"
| 20 | 790 | 645 | 530 | 350 | 130 | 66.5 |