1/4" CE Phenolic is used for the interstage coupler rings and plates.

.250" G&P 303 Stainless Steel guide rods & 5/16"o.d. x .32w. brass guide tubes with rings & plates.
The rings are bored for 38mm phenolic motor mount tube.

The upper stage guide tube assembly and the lower stage guide rod assembly.

The guide rod assembly mounts in the booster transition piece.
The guide tube assembly mounts in the second stage fin can.

The upper and lower brass tubes are reamed to .2515" prior to lapping.

The guide rods and tubes have been carefully lapped with a fine abrasive compound to assure a smooth and accurate fit.
the fit is so smooth that when the parts are assembled dry (without lubricant)and the assembly is picked up by the second stage fin can, the booster transition will slowly slide out of the guide tubes mounted in the fin can.