A delivery tool including a shaft and a proximal capsule and a distal capsule is dimensioned for percutaneous delivery to the heart. An open end of the proximal capsule faces the open end of the distal capsule. The capsules are coupled to the shaft in a manner that allows axial movement of the capsule with respect to the shaft. A prosthetic heart valve includes a tubular portion that defines a lumen and prosthetic leaflets disposed within the lumen. The prosthetic heart valve is restrainable in a compressed state by the delivery tool, such that a downstream end of the tubular portion is disposed within the distal capsule. The distal capsule is shaped so as to define an opening for visualizing ensheathing of at least a portion of the downstream end of the tubular portion within the distal capsule. Other embodiments are also described.