All Morters are HDPE (High density polyEthylene ) The standard for safety in the fireworks industry. 1.91 average inside diameter, 12 Inch lenght, 10.5 inside length. ALL MORTER TUBES COME PLUGGED! Wall thickness is .25. Lenght is 12. This is the most common size as it will have a perfect fit for all Excallibur and Lock N LOAD shells (consumer) and most all commercial 2 shells. Cared for properelly, these will last a lifetime of use.