Cold-rolled steel lapping tool chucks into a 3/8" hand drill to easily
“square” the upper receiver face on your AR-15. Helps ensure
precise mating of barrel and receiver for added accuracy. Coat face
of receiver with aluminum-oxide lapping compound; extra long pilot
slides into the bolt carrier tunnel to maintain perfect concentricity
with the receiver.
SPECS: Cold-rolled steel, in the white. 8¼" (21cm) long,
3/8" (9.5mm) diameter shank.
Catalog page 73