To the best of my knowledge, g-4 is not a chain designation used on gypsies. I've seen BBB, HT and a few others, and of course sized to your chain. When we bought our new windlass the retailer assured us that the 3/8" HT designation would handle 3/8" BBB. Needless to say, it wouldn't and it took several months to get the right gypsy. The retailer did not understand the gypsy numbering system, so they ordered the wrong one twice. At least these were all their mistakes, so all it cost us was time. Be extremely careful to order the correct gypsy, if you order the wrong one you might get stuck with it, and still need the correct gypsy.