When we ran a full service chassis fab/turn-key hot rod shop a number of years ago, it was always useful to have threaded things around to weld into the frame for some kind of mount, etc.
Here’s a list of all our threaded things for your reference:
Spacer; 1" OD x 16mm ID x 2"
Product Details
Brand: Welder Series
MPN: 212321
Bolt Size: 5/8"
Diameter: 1"
Length: 2"
Used in our rear coil over crossmember kits. 16mm is clearance for a 5/8" bolt.