{"product_id":"castair-replacement-air-filter-element-for-d3-d31-d4-rotary-pumps-2-7-8id-x4-5-8od-rafd3-4","title":"Castair Replacement Air Filter Element For D3,D31,D4 Rotary Pumps 2 7\/8\"ID.X4 5\/8\"OD. RAFD3-4","description":"\u003ch2\u003eCastair Replacement Air Filter Element for D3, D31, D4 Rotary Pumps (RAFD3-4)\u003c\/h2\u003e\n\n\u003cp\u003eThe Castair RAFD3-4 is the paper air filter element for D3, D31, and D4 rotary screw pump air ends, covering the 5 to 10 HP range of Castair rotary screw compressors. Dimensions: ID 2-7\/8\", OD 4-5\/8\", HGT 2-7\/16\". This is one of the smaller filter elements in the Castair lineup, sized for the compact air ends used in 5-10 HP machines. At $21.18, it is an inexpensive part that directly affects air end longevity — running a rotary screw compressor with a dirty or restricted filter damages the air end over time and is not recoverable through maintenance after the fact.\u003c\/p\u003e\n\n\u003cp\u003eThe D3, D31, and D4 designations refer to different variants in the same pump family used across Castair's lighter-duty 3-phase rotary screw models. All three use the same RAFD3-4 filter element — check your compressor nameplate for the air end model to confirm you are in the D3\/D31\/D4 family before ordering.\u003c\/p\u003e\n\n\u003ch3\u003eFilter Specifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart number:\u003c\/strong\u003e RAFD3-4\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFilter type:\u003c\/strong\u003e Paper element, dry-type\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInside diameter (ID):\u003c\/strong\u003e 2-7\/8\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOutside diameter (OD):\u003c\/strong\u003e 4-5\/8\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHeight (HGT):\u003c\/strong\u003e 2-7\/16\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e D3, D31, and D4 rotary pump air ends\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHorsepower range:\u003c\/strong\u003e 5-10 HP Castair rotary screw compressors\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eAir End Filter Cross-Reference\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRAFD3-4 (this part):\u003c\/strong\u003e D3, D31, D4 — 5-10 HP — ID 2-7\/8\", OD 4-5\/8\", HGT 2-7\/16\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRAFD6-62:\u003c\/strong\u003e D6, D62 — 15-25 HP — ID 4-3\/4\", OD 6-1\/8\", HGT 2-7\/8\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRAFD10:\u003c\/strong\u003e D10 — 25-40 HP — ID 6-3\/8\", OD 9-1\/2\", HGT 5\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRAFD16:\u003c\/strong\u003e D16 — 50-60 HP — ID 6-3\/8\", OD 9-1\/2\", HGT 7-7\/8\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRAFG11:\u003c\/strong\u003e G11 — 5-15 HP — ID 2-5\/8\", OD 3-7\/8\", HGT 3-1\/8\"\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eMaintenance Schedule\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eVisual inspection:\u003c\/strong\u003e Check at every oil change — more frequently in dusty environments\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHour meter:\u003c\/strong\u003e Your Castair compressor has an hour meter standard — use it to track filter intervals\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePM kit option:\u003c\/strong\u003e MKD3-4 includes 2 RAFD3-4 air filters, 4 oil filters, 1 separator filter, 5 gal CAST-LUBE oil — saves 10% vs. individual purchases and covers the D3, D31, and D4 air end families\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat Is in the Box\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e1x Castair RAFD3-4 paper air filter element\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCastair authorized:\u003c\/strong\u003e OEM filter with confirmed dimensions\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree tech support:\u003c\/strong\u003e 866-217-0063 — confirm your air end model if you are unsure\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFull lineup in stock:\u003c\/strong\u003e All Castair rotary pump filter elements available\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342584209621,"sku":"RAFD3-4","price":39.76,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/360_F_473254957_bxG9yf4ly7OBO5I0O5KABlN930GwaMQz_3b548261-25b2-4db7-90b6-b0b6eecfa74a.jpg?v=1772652858","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-replacement-air-filter-element-for-d3-d31-d4-rotary-pumps-2-7-8id-x4-5-8od-rafd3-4","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}