This fin can unit is meant to be as close a copy as possible to the ones used in the Centuri model rocket kits

Screaming Eagle (kit #KF-3, 1973-1983) and
Spartan (kit #KD-3, 1976 Stellar Series)

that fits the original ST-8 airframe tubing. It has an integrated engine hook channel designed into it as well as a motor mount tube block similar to the original design.

There are stock two versions - one with and one without integrated fillets on the fins.
Two more stock versions include a filleted and non-filleted, integrated, 3/16" (4.76mm) launch lug.
Two versions have an extended, integrated tubing coupler that are filleted and non-filleted.
Two versions have an extended, integrated tubing coupler with 3/16" integrated launch lug that are filleted and non-filleted.

JimZ info page.
http://www.spacemodeling.org/jimz/kf-3.htm

Screaming Eagle in the 1973 Centuri catalog.
http://www.ninfinger.org/rockets/nostalgia/73cen70g.html
Screaming Eagle in the 1983 Centuri catalog.
http://www.ninfinger.org/rockets/catalogs/centuri83/83cen4.html
Spartan 1976 in the Spring Stellar Series Centuri catalog.
http://www.ninfinger.org/rockets/catalogs/centuriRT76Spring/76SpringcenRT10.html
Spartan 1976 in the Fall Stellar Series Centuri catalog.
http://www.ninfinger.org/rockets/catalogs/centuriRT76Fall/76FallcenRT6.html

Screaming Eagle build article:
Kit background
http://modelrocketbuilding.blogspot.com/search/label/C%20Screaming%20Eagle
Part 1
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-1.html
Part 2
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-2.html
Part 3
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-3.html
Part 4
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-4.html
Part 5
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-5.html
Part 6
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-6.html
Part 7
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-7.html
Part 8
https://modelrocketbuilding.blogspot.com/2014/08/centuri-screaming-eagle-build-part-8.html

RockSim file available at RocketReviews.
https://www.rocketreviews.com/rocksim-centuri---screaming-eagle.html

Centuri ST-8 tubing is available for purchase at eRockets.
http://www.erockets.biz/st-8/

PNC-89 nose cone for the Screaming Eagle and Spartan by 'dholvorson.'
https://www.thingiverse.com/thing:576222

Picture is an upscaled Screaming Eagle 2.9x by Randy Gilbert designed to fly on F-G 29mm rocket motors. Airframe diameter is 2.6 inches (66.04mm) and total length is 47.8 inches (1214.12mm or 1.21m). Graphics were upscaled printed on Papilio Silver Adhesive Polyester film on an inkjet printer.