Metallics G8HC75334 Bolt 3/4-10 x 3-3/4 G8 HXBT St-YZn (20 pcs)

It's a 3/4-10 x 3-3/4 inch hex bolt. That's a 3/4 inch diameter with 10 threads per inch (UNC coarse), and 3-3/4 inches of length measured from under the head. Pairs with a standard 3/4-10 heavy hex or finished hex nut.

Yes, G8 means SAE Grade 8 medium carbon alloy steel, quenched and tempered. Grade 8 is the higher-strength structural choice over Grade 5, which is why it gets specified for equipment mounting, machine bases, and heavy anchorage where a Grade 5 fastener would be undersized. Grade 8 is identified in the field by six radial lines on the head.

The bolt is steel with a yellow zinc plating (St-YZn). Yellow zinc gives better corrosion resistance than clear zinc and is fine for dry interior work, protected mechanical rooms, and covered exterior locations. For direct weather exposure, submerged, or coastal use, a hot dip galvanized or stainless fastener is the better call. Note that zinc plated Grade 8 should not be mixed with aluminum or galvanized members where dissimilar metal corrosion is a concern.

Each pack is 20 bolts. If you're ordering for a job with a fixed bolt count, work in multiples of 20 so you're not short a few on the last connection. Nuts and washers are separate items, not included.

Go Grade 8 when the connection is torqued high, carries vibration or cyclic load, or the engineer called out Grade 8 on the drawing. The G8HC75334 is a 3/4-10 Grade 8. Grade 5 is adequate for general bolting and is more forgiving, but it cannot be substituted where Grade 8 is specified. Substituting the other direction (Grade 8 in place of Grade 5) can also be wrong on connections designed to yield, so follow the detail rather than upgrading on your own.