ID (inner dimensions) vs. OD (outside dimensions)

We distinguish between the two -- and list them separately -- because both are important to the usability of the mold you choose. Each product page lists both sets of dimensions in the description. On larger molds we also provide the diagonal measurement.

The charts below demonstrate how we determine those measurements.

We also offer a comparison chart of all molds -- by inner dimension -- to help you easily choose the best size for your project.

Mold Size Chart

Inner Dimensions

Inner dimensions reflect the cavity of the mold and indicate the size resin blank the mold will produce (height, width & length). This information helps you choose the right size mold for your project based on the blank you're trying to create.

On all molds, we provide a 1/4" of overpour room to make it easier to transfer the mold to the pressure pot without spilling. Height reflects the measurement without the overpour.

Outer Dimensions

Outer dimensions reflect the overall size of the mold itself (height, width & length), including the bolts & wing nuts that protrude from one or both ends. This information -- along with the diagonal measurement -- is important if you're considering whether or not a mold will fit into your pressure pot. If you're using open casting methods (no pressure pot), these details are less important.

Diagonal Measurement

Diagonal measurement (corner to corner with extra allowance for the bolts) indicates the minimum pressure pot inside-diameter needed for the mold to fit.

Why the Diagonal Measurement Matters:

If your pressure pot's inside diameter is 9", an 8.75" long mold will not fit inside the pot because you're not placing the longest measurement at the center of the circle. You also have to consider the impact of the mold width and the presence of hardware.

Our 6-pack pen mold, for example, is 8.75" long x 7.75" wide. It takes a pot with an inside-diameter of 11.75" to hold the mold if the pot is placed in a typical upright position.* The mold would not fit a 2.5 gallon pot (typically just over 9") but it would probably fit a 5 gallon pot (typically just over 12").

*Using the Pressure Pot Horizontally:

In some cases, if the mold is just a little too large, the solution could be as simple as placing the pressure pot on its side.

A pressure pot will function as intended whether horizontal or vertical.

Place the pot on its side with the opening facing you. Pull it forward on the workbench until the latch hardware hangs off the front, keeping the body level from front to back.
Stabilize the pot so that it can't roll during operation.
Slide the mold into the pot.
Attach the lid, taking care not to roll the pot or drop the lid. (It will be an awkward process the first time.)
Set the controls and continue as normal.

Some resin casters have built mounting cradles to keep the pot level and stable. Others have installed horizontal pots permanently on their workbenches to keep the larger casting environment readily available.

Mold Size Chart (by inner dimensions)