Crosslinkable compositions comprising mixtures comprising at least two different compounds of the formula Y-[NH-C(=O)-NR 3 -(CR 1 2) b -SiR a (OR 2) 3-a] x, where Y is an x-valent organic radical, R 3 may be identical or different and is hydrogen atom, a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, a group -(CR 1 2) b -SiR a (OR 2) 3-a or a group -CH(COOR')-CH 2 -COOR', R' may be identical or different and is a monovalent, optionally substituted hydrocarbon radical, R may be identical or different and is a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, R 1 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur, or carbonyl group, R 2 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1, or 2, and b may be identical or different and is an integer from 1 to 10, with the provisos that some of the radicals Y contain at least one urethane group and/or urea group and also at least one polyether group and/or polyester group, and that more than 50% of all the urethane groups and urea groups which are present in the compounds of the formula in the mixture are urea groups which are part of an end group of the formula -NH-C(=O)-NR 3 -(CR 1 2) b -SiR a (OR 2) 3-a, optionally polymers which do not conform to the formula, basic nitrogen-containing organosilicon compounds in amounts of from 0.1 to 25 parts by weight, based on 100 parts by weight of component, optionally fillers, optionally silicone resins, optionally catalysts, optionally adhesion promoters, optionally water scavengers, optionally nonreactive plasticizers, optionally additives, and optionally adjuvants. mixtures comprising at least two different compounds of the formula Y-[NH-C(=O)-NR 3 -(CR 1 2) b -SiR a (OR 2) 3-a] x, where Y is an x-valent organic radical, R 3 may be identical or different and is hydrogen atom, a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, a group -(CR 1 2) b -SiR a (OR 2) 3-a or a group -CH(COOR')-CH 2 -COOR', R' may be identical or different and is a monovalent, optionally substituted hydrocarbon radical, R may be identical or different and is a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, R 1 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur, or carbonyl group, R 2 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1, or 2, and b may be identical or different and is an integer from 1 to 10, with the provisos that some of the radicals Y contain at least one urethane group and/or urea group and also at least one polyether group and/or polyester group, and that more than 50% of all the urethane groups and urea groups which are present in the compounds of the formula in the mixture are urea groups which are part of an end group of the formula -NH-C(=O)-NR 3 -(CR 1 2) b -SiR a (OR 2) 3-a, optionally polymers which do not conform to the formula, Y is an x-valent organic radical, R 3 may be identical or different and is hydrogen atom, a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, a group -(CR 1 2) b -SiR a (OR 2) 3-a or a group -CH(COOR')-CH 2 -COOR', R' may be identical or different and is a monovalent, optionally substituted hydrocarbon radical, R may be identical or different and is a monovalent, optionally substituted, SiC-bonded hydrocarbon radical, R 1 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur, or carbonyl group, R 2 may be identical or different and is hydrogen atom or a monovalent, optionally substituted hydrocarbon radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1, or 2, and b may be identical or different and is an integer from 1 to 10, basic nitrogen-containing organosilicon compounds in amounts of from 0.1 to 25 parts by weight, based on 100 parts by weight of component, optionally fillers, optionally silicone resins, optionally catalysts, optionally adhesion promoters, optionally water scavengers, optionally nonreactive plasticizers, optionally additives, and optionally adjuvants.