RCBS #90310. RCBS Case Trimmers are designed to be user friendly and provide very accurate results. These shellholders are required to hold the brass cases while they are being trimmed. Works with: RCBS Trim pro, manual and power case trimmer only. Fits: 17 Remington, 204 Ruger, 221 Remington Fireball, 222 Remington, 222 Remington Magnum, 223 Remington, 7mm TCU (Thompson/Center Ugalde), 380 ACP.