See attached ORK file:

• The body tube is 15" long. Calculated mass is .827 oz.
• The tube fins are a set of 5, each 3" long. Calculated mass is 4.3 oz.
• Both are based on the same library component (BMS T60-34).

There seems to be an extra multiplication by the number of fins (i.e. the mass of one fin is getting multiplied by 5 twice). Pretty much confirmed this by experimenting with the number of fins in the set.

tube_fins_mass.zip