Scale: 1/48

Set includes four Mk.8 torpedo warhead inserts.

Also available:
set of two forward torpedo tubes 
set of two aft torpedo tubes 
set of four torpedo tube breech doors (if you buy the tubes, breech doors are not needed)
PT-109 nameplate (from Shapeways)
 
Recommended for:
Bluejacket Shipcrafters 1/4" = 1' (1/48) scale "80' Elco PT Boat"
Merit International 1/48 scale Elco 80' Motor Patrol Torpedo Boat  Late Type
Merit International 1/48 scale Elco 80' Motor Patrol Torpedo Boat  Early Type
 
These parts represent the exposed warhead of the Bliss-Leavitt Mk.8 torpedo fired from US Navy PT boats, among other USN and Royal Navy Lend-Lease-procured vessels, during World War Two.  When loaded into the torpedo tube, the Mk.8's domed warhead was exposed.  
 
A good reference for PT boats can be found on NavSource (click here).

These parts are not 3D-printed copies of any plastic model kit's parts.  They are sized to fit the Model Monkey torpedo tubes available separately.  Therefore, they may not be the same size or shape of your plastic kit's parts and may not fit your plastic kit's torpedo tubes.  Depending on which plastic kit you own, some adjustment of the plastic kit's parts may be needed for best fit.

© Model Monkey LLC.  This 3D-printed item may not be copied or recast.

From Wikipedia: "The Bliss–Leavitt Mark 8 torpedo was the United States Navy's first 21-inch by 21-foot torpedo.  Although introduced prior to World War I, most of its combat use was by PT boats in World War II. The torpedo was originally designed in 1911 by Frank McDowell Leavitt of the E. W. Bliss Company and entered full mass production in 1913 at the Naval Torpedo Station in Newport, Rhode Island. It was deployed on destroyers and battleships during World War I and cruisers built in the 1920s. All US battleships and most cruisers had their torpedo tubes removed by 1941. The Mark 8 remained in service through World War II on older destroyers, primarily the Wickes and Clemson classes. It also equipped PT boats early in World War II, but was replaced by the Mark 13 torpedo on most of these in mid-1943.

"Under the Lend-Lease Act, about 600 Mark 8 torpedoes were issued to the United Kingdom for use with 50 pre-1930 destroyers it received under the Destroyers for Bases Agreement."