A unit for use with an image forming apparatus includes: a frame; a developer accommodating portion; a sheet member, contact to a rotatable member and provided on the frame along a longitudinal direction of the rotatable member; a first end portion seal member for preventing, at a longitudinal end portion, the developer from leaking out from between the frame and the rotatable member; and a second end portion seal member for preventing the developer from leaking out from among the first end portion seal member, the sheet member and the frame. The second end portion seal member is formed by injecting, on the frame, a resin material having an elastic modulus smaller than an elastic modulus of the frame so as to contact with the first end portion seal member and the sheet member.