Check the listing for details. BT-70 X 29mm Centering Ring Set For Estes model rocket kits laser cut ply.. Condition: New. Listed at 2.50 USD. BT-70 X 29mm Centering Ring Set For Estes model rocket kits laser cut ply. Condition is "New". Shipped with USPS First Class. This is a pair of laser-cut plywood centering rings for BT-70 body tubes to mount 29mm motor tubes (E through G power). Included are two rings precision cut form 1/8" baltic birch plywood - for a super strong mount. This auction only includes the rings, tubes in the pictures are for illustration only. Fits Estes BT-70 tubes and Heavy-wall tubing from Balsa Machining. Should fit most manufacturers tubes. Don't see the size centering ring you want? Contact me, I can probably make it. Thanks for looking.Combining orders? Contact me about combined shipping or request a shipping discount in your check-out note!