The lens is faulty because the focus button is jammed permanently on so is being sold for spares or repair.
eBay
NEW Professional Camera Bag Camera Case Backpack For CANON SONY NIKON 400mm 500mm T41
Aliexpress UK
The edge is treated with fine edge wrapping to prevent edge loss and warping. Three focus lock buttons. The surface of the fabric is treated with anti-splashing water. Close fit, easy to disassemble and assemble.
eBay
Lens Support Collar Tripod Mount Ring Replacement Base Foot Stand for Sony FE 400mm 600mm F/2.8 GM
Aliexpress UK
The edge is treated with fine edge wrapping to prevent edge loss and warping. Three focus lock buttons. The surface of the fabric is treated with anti-splashing water. Close fit, easy to disassemble and assemble.
eBay
NEW Camera Bag Camera Case Backpack For CANON NIKON OLYMPUS SIGMA SONY 400mm-800MM Lens Case 4316
Aliexpress UK
The edge is treated with fine edge wrapping to prevent edge loss and warping. Three focus lock buttons. Top button open.
eBay
Specifically designed and made of this lens. Can be installed with or without the hood in place. Works with hood reversed.
eBay
The lens cover is designed for use with Sony FE 400mm f2.8 GM OSS lenses.
eBay
Original Sony SEL100400GM lens. Original Sony lens hood. Original removable tripod lens foot. Original lens bag. Excellent, like new – used only once. Fully functional. There are a couple ofpin-needle-sized marks on the hood (see photos), but otherwise in top condition.
eBay
[MINT+++] sony FE 400mm f/2.8 GM SEL400F28GM AF Telephoto Lens For E Mount JAPAN #4727 The nameplate has a slight scratch, but otherwise, it is in beautiful, almost unused condition. All you can see on the picture will be included in a set of a package. Weekends are not available because office is closed. Customer service and satisfaction are very important to us. I have an unconditional return policy if notified within 30 days of the receipt of the item. All return requests must be made within 30 days of the receipt of the item. Please contact me first for return before you ship it back to me. Import duties, taxes, and charges are not included in the item price or shipping cost. Please check with your country's customs office to determine what these additional costs will be prior to bid.
eBay